Boston ( CNN ) -- As the horror of explosions near the finish line of the nation 's most famous marathon sank in , government officials mobilized to respond on Monday afternoon . FBI director Robert Mueller briefed President Barack Obama by telephone , the White House said . All off duty-police officers in Boston were told to report to their districts , CNN affiliate WHDH reported , and the Red Cross sent additional blood products to Boston-area hospitals , spokeswoman Anne Marie Borrego said . Aviation authorities banned planes from flying over of the site of the explosion , the Federal Aviation Administration said . The temporary flight restriction came at the request of law enforcement and originally extended three nautical miles in all directions before being reduced to two . It reaches up to a height of 3,000 feet , FAA spokeswoman Arlene Salac said . The agency ordered a brief ground stop at Boston 's Logan airport but it did not last long . Get up-to-the-minute updates on our live blog . And law enforcement authorities from Atlanta to San Francisco and Seattle said they were on heightened alert . New York 's Mayor Michael Bloomberg said the city had 1,000 officers assigned to counterterrorism duties , `` and they -- along with the entire NYPD and the investments we have made in counterterrorism infrastructure -- are being fully mobilized to protect our city . '' In Miami , police said they were increasing security at critical infrastructure sites , while the Los Angeles Police Department restated its advice to the public : `` If you see something , say something . '' Secretary of State John Kerry -- a former Massachusetts senator with deep ties to Boston -- found out about the blasts when he was on his way to Chicago on his way home from a 10-day foreign trip , and called his daughter Vanessa , who has run the Boston Marathon in the past , a senior State Department official said . Detailed map of attack area . Kerry himself often fires the starting gun for the wheelchair race at the marathon . Attorney General Eric Holder instructed the Justice Department to deploy its `` full resources '' to the investigation into the blasts that killed at least two people and left dozens injured . He spoke to FBI director Mueller , and to the U.S. Attorney for the District of Massachusetts , Carmen Ortiz . Her office is coordinating responses from the Justice Department , the FBI , the Bureau of Alcohol , Tobacco and Firearms and other law enforcement officials . Homeland Security Secretary Janet Napolitano was briefed , and she ordered her department to provide `` whatever assistance is necessary '' to state and local authorities , an administration official said . The House of Representatives announced it would hold a minute 's silence to honor the victims of the explosions . London 's Metropolitan Police said they were reviewing security arrangements for the London Marathon , which is due to take place on Sunday . The race 's chief executive , Nick Bitel , said organizers were `` deeply saddened and shocked , '' and called it `` a very sad day for athletics and for our friends and colleagues in marathon running . '' British Foreign Secretary William Hague said he was `` appalled '' by the explosion , while Canada 's Prime Minister Stephen Harper said : `` It is truly a sad day when an event as inspiring as the Boston Marathon is clouded by such senseless violence . '' Major League Baseball senior public relations executive Pat Courtney said the League 's `` thoughts and prayers are with everyone affected by this horrible occurrence . '' The Red Sox were playing in Boston on Monday but the game was over before the terror attack . Eyewitness : People hurt very badly . CNN producer heard big boom , saw smoke . From CNN Chief White House Correspondent Jessica Yellin , CNN Senior Producer Carol Cratty and CNN Producer Mike Ahlers .
NEW : Barack Obama checks in with his daughter , who has run the marathon in the past . NEW : Canada 's prime minister laments an `` inspiring event clouded by senseless violence '' Police from London to Los Angeles on heightened alert ; off-duty Miami cops called in . Boston police say they are reviewing security for the city 's marathon on Monday .