Add a location to your Tweets 
 
 When you tweet with a location, Twitter stores that location. You can switch location on/off before each Tweet and always have the option to delete your location history. Learn more ||||| CAMBRIDGE — Joe Palana had just sat down for the last exam of his first semester at Harvard Monday when alarm bells pierced the silence at Emerson Hall. Like others around him, the freshman from Rockland thought it was just a fire drill, so he left his bag. But he grabbed his coat. 
 
 That made him luckier than some of the hundreds of Harvard students and faculty who were displaced at 9 a.m. by a bomb scare and walked out in their shirtsleeves or without their university ID cards, only to be locked out for hours as law enforcement swept the campus over what officials called “unconfirmed reports of explosives.” 
 
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 Police ultimately found no suspicious devices, but the threat, which officials said came via e-mail, drew an array of emergency responders and a throng of reporters to Harvard, eight months after the attack on the Boston Marathon. In Washington, President Obama was briefed. 
 
 Related Photos Police investigate reports of explosives at Harvard 
 
 But the mood on campus seemed to shift quickly from fear toward curiosity, annoyance, or indifference, long before the last of the four evacuated buildings was deemed bomb-free around 3 p.m. Almost from the start, officials called the evacuation a result of “an abundance of caution,” and many students speculated that the threat was an exam-period hoax. 
 
 “My guess is someone is trying to cause mischief during finals week,” said Nathan Pflueger, a graduate student who had just arrived at his office at the Science Center when the alarm went off, prompting a mass exodus. 
 
 “Ten-to-one it’s an obnoxious effort to stop an exam today,” said sophomore Connor Harris, standing outside the center five hours later, yellow caution tape and a cluster of emergency vehicles still blocking the entrance. 
 
 Harris said the atmosphere was “nothing like” that of last April, when the university and surrounding area was on lockdown during the manhunt in Watertown for the Marathon bombing suspects. “People were quite frightened” then, he said. 
 
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 But possibly because it took place at Harvard, the threat Monday made news worldwide. Harris awakened to read not just a university emergency alert message but also a text from his parents in Connecticut, hoping he was safe. Standing on the blocked-off end of Kirkland Street, he read a news story on his phone about the threat, in German, on the website of Der Spiegel. 
 
 The threat targeted Emerson, Thayer, and Sever halls in Harvard Yard and the Science Center, just beyond the yard. 
 
 Thayer and Emerson reopened after four hours, Sever after five, and the Science Center after six hours, though a heightened police and security presence remained well into the afternoon. 
 
 After the evacuation, officials closed Harvard Yard to the public, restricting access to those with university IDs. 
 
 By 11, a few dozen students were waiting along Massachusetts Avenue to return through one of the limited-access gates. Despite the helicopters overhead and the power cords for satellite trucks running down the sidewalk, the mood was the usual end-of-semester mix of jubilation and anxiety, with little evident fear. 
 
 Michael Casciotti, shivering in shorts and flip-flops, was just trying to stay warm. 
 
 “I’m very cold,” said the freshman from Pennsylvania, who had ventured barefoot and bleary-eyed from his Thayer dorm room into the hall at the sound of the alarm. 
 
 “I left all my stuff in there, didn’t have any clothes on, so my friend gave me a sweater and flip-flops,” he said. 
 
 As the three-hour mark approached, Palana, the freshman from Rockland, remained displaced from his bag and his dorm room, in Thayer. He had decamped for an upperclass dorm far from the yard — “I wasn’t too concerned, [but] I had some friends that were pretty scared” — but wandered back toward Harvard Yard for lunch, spotting a friend waving from the third floor of a dorm just inside the gate. A federal Homeland Security sport utility vehicle had just raced past, sirens blaring. But the friend, shirtless, appeared unconcerned. 
 
 “Hey, Adam!” Palana called. “You look not very cold. It’s not so warm out here.” 
 
 Palana glanced at his phone and saw an update: His exam had been rescheduled for a choice of 6:30 p.m. Monday night or the third week of next semester. 
 
 His classmate Emma Woo cringed; Monday’s new timing coincided with her chorus concert, so she would have to study again over break. “Dude, that’s the worst,” Palana said. 
 
 A Harvard e-mail advised students that afternoon exams would be held as scheduled, with exams in affected buildings moved but not canceled. 
 
 The Faculty of Arts and Sciences message advised students that if they felt unable to take their exams for any reason, “including anxiety, loss of study time, lack of access to material and belongings left in one of the affected buildings, or travel schedule,” they could skip the exam and take a grade based on coursework to date. 
 
 That prompted a group of graduate students to begin drafting a reply cautioning that the approach would “set up a new and dangerous precedent on campus, that bomb threats will get students out of final exam responsibilities.” 
 
 “We see the note as analogous to negotiating with terrorists,” doctoral student Alek Chakroff said in an e-mail to the Globe. “We sympathize with students who are distressed by the threats, especially in the wake of the Marathon bombings. But in responding to these threats, we think excusing students from exams should be the exception, not the rule.” 
 
 A subsequent Harvard e-mail reiterated the policy for students who skipped Monday afternoon exams but clarified that anyone who felt unable to take another exam this week as a result of the bomb threat would need evaluation and documentation from student mental health services. ||||| In the Event of an Emergency 
 
 The campus community will be notified through a variety of mechanisms including the Web, email and voicemail. 
 
 The Harvard homepage will broadcast an alert and direct users to an emergency page outlining the University's response. There will also be messages on the University's 24-hour news line, (617) 496-NEWS (496-6397). 
 
 Harvard University Police Department (HUPD) ||||| Add a location to your Tweets 
 
 When you tweet with a location, Twitter stores that location. You can switch location on/off before each Tweet and always have the option to delete your location history. Learn more ||||| Students enter Emerson Hall to take their final examinations after it had been deemed safe by University officials. 
 
 UPDATED: December 17, 2013, at 3:05 a.m. 
 
 An apparently unfounded emailed threat of live explosives in three academic buildings and one dormitory near the center of Harvard’s campus on Monday morning prompted exam cancellations in several large courses, the descent of federal, state, and local law enforcement, and a White House briefing. 
 
 Hundreds of Harvard College students were prematurely roused from bed or abruptly interrupted from their final examinations shortly after 9 a.m., when Harvard University Police sounded alarms in four campus buildings. The evacuations of the Science Center, Emerson Hall, Sever Hall, and Thayer Hall sent scores of students into Harvard Yard and the Science Center Plaza, leaving police to search the premises. With the developing situation attracting national media attention, little happened as a nearly six hour investigation yielded no explosive contraband and authorities issued the all-clear shortly before 3 in the afternoon. 
 
 According to department spokesperson Steven G. Catalano, the threat came in an emailed message to an affiliate of HUPD that was timestamped, according to Executive Vice President Katherine N. Lapp, at 8:40 a.m. 
 
 A Harvard spokesperson who declined to be identified confirmed that the email received by the HUPD affiliate was “nearly identical” to an email received at 8:45 a.m. by Crimson President Robert S. Samuels ’14. Under the subject line “bombs placed around campus,” the email to Samuels read, “bombs placed in: science center [and] sever hall [and] emerson hall [and] thayer hall. 2/4. guess correctly. be quick for they will go off soon.” 
 
 After the HUPD affiliate read the emailed threat, the department immediately dispatched officers because the email specifically named its targets, according to the Harvard spokesperson. Simultaneously with the dispatch, the spokesperson said, HUPD drafted a MessageMe alert to the Harvard community, the first of more than 10 emails that College students would receive from Harvard officials throughout the day. Repeatedly in those messages, administrators stressed that they were acting out of an “abundance of caution” in an effort to keep the campus community safe. 
 
 By the time that first MessageMe alert was sent at 9:02 a.m., HUPD officers had already started evacuating the targeted buildings. Another alert, at 9:13 a.m., reported that HUPD and Cambridge Police were on the scene and investigating. By noon, state and federal authorities had arrived on the scene, and President Obama had been briefed on the situation, according to a White House spokesperson. 
 
 Not long after the building evacuations, authorities closed Harvard Yard. Students evacuated from the Science Center who had initially thought the disturbance was nothing more than an ill-timed fire drill were directed to an Annenberg Hall that quickly overflowed from the combination of the usual breakfast rush and those displaced from exam rooms and bedrooms. 
 
 Dean of Undergraduate Education Jay M. Harris soon joined the students in Annenberg, where he would later be joined by University President Drew G. Faust and interim College Dean Donald H. Pfister. After discussing the situation with a number of teaching staff, Harris climbed on a table and announced that all of the exams scheduled that morning in the three affected classroom buildings had been cancelled. During his impromptu speech, Harris did not settle definitively the question of whether cancelled exams would need to be made up. 
 
 Throughout the morning, students with exams scheduled for the day received emails from teaching fellows and professors, many of whom expressed uncertainty about how their courses would be graded, and if students would be required to make up exams. With three major academic buildings still shuttered, students slated to sit for finals at 2 p.m. were cast into an uncomfortable holding pattern. Just after 12 p.m., the University notified parents of undergraduates of the ongoing situation. 
 
 With the search turning up no evidence of explosives, life in the Yard began to return to normalcy as the day progressed. The Yard reopened to Yard residents before 11 a.m. And, at 12:40 p.m., Securitas guards stood by Johnston, Widener, Lamont, and the Science Center gates, allowing Harvard ID holders into the Yard. Shortly before noon, several dozen students could be found studying in Lamont Cafe, as well as in Lamont’s reading rooms. At least three others had fallen asleep, some at tables, others on couches. 
 
 Early in the afternoon, HUPD sent out alerts announcing that Emerson and Thayer, and then Sever and Harvard Yard, were safe for return, but officers continued to search the Science Center, forcing the cancellation of afternoon exams set to be held there. In an email to undergraduates just minutes before 2 p.m. exams were scheduled to start, Administrative Board Secretary John “Jay” L. Ellison wrote that any students who felt unprepared to take their still-scheduled afternoon exams could be excused from the sitting. 
 
 Those who opted to forgo uncancelled afternoon exams, Ellison wrote, could choose to be graded on coursework to date, excluding the final, or to be evaluated on a pass/fail basis without penalty. In an email later in the afternoon, Ellison reiterated that the rest of the week’s exams remained scheduled. 
 
 Authorities finally cleared the Science Center at 2:44 p.m., effectively declaring an end to the campus scare. As of press time, Catalano would not comment on whether the investigation had turned up any suspects. 
 
 —Antonio Coppola, John P. Finnegan, and Dev A. Patel contributed to the reporting of this story. 
 
 —Staff writer Matthew Q. Clarida can be reached at matthew.clarida@thecrimson.com. Follow him on Twitter @MattClarida.
– Harvard University has reopened four buildings on campus after evacuating them this morning due to a bomb scare, the Harvard Crimson reports. Sever Hall, Thayer Hall, and Emerson Hall were all cleared in time for afternoon exams, and Harvard Yard was reopened before 2pm. An email tip prompted the threat, reports the Boston Globe, but a Harvard police spokesman refused to confirm. No explosives have yet been found. The school posted alerts on its emergency page and its Twitter account, clarifying that there were no reports of actual explosions, and that the evacuations were ordered out of an "abundance of caution."