( CNN ) -- The Department of Homeland Security has ordered U.S. Customs and Border Protection agents to verify , `` effective immediately , '' that every foreign student who wants to enter the United States has a valid student visa , a U.S. government official told CNN on Friday . The memo went out earlier this week as part of an effort to reform the student visa system , said the official , who spoke on condition of anonymity . The effort is meant to provide the agency with real-time updates on all relevant information , the official said . News of the memo follows reports that two friends of Boston Marathon bombing suspect Dzhokhar Tsarnaev , who are now charged in connection with the attack , may have been in the country on student visas that were no longer valid . Dias Kadyrbayev and Azamat Tazhayakov , both 19 and from Kazakhstan , were charged this week on suspicion of obstruction of justice in connection with the case . They were already in federal custody on suspicion of violating the terms of their student visas when they were charged in the bombings case . The pair started at the University of Massachusetts Dartmouth in 2011 , along with Tsarnaev . Kadyrbayev was not enrolled at the time of his arrest last month . His lawyer , Robert Stahl , told CNN his client had not been attending classes on a regular basis , as required by his visa . Tazhayakov 's student status is less clear . According to the university , Tazhayakov is enrolled but was suspended pending the outcome of the current case . At an immigration court hearing this week , however , the court heard that Tazhayakov 's status with the school was terminated January 3 , according to a U.S. government official . The court also heard that Tazhayakov went to Kazakhstan in December 2012 and was allowed to return to the United States on January 20 , despite the apparent lapse in his visa status , the same government official said . That news has outraged U.S. Rep. Michael McCaul , head of the House Committee on Homeland Security . `` The fact that a foreign national was able to re-enter the U.S. with what appeared to be a valid student visa , while Customs and Border Protection officers were unaware that his visa status had become invalid , represents a serious hole in our national security , '' McCaul told CNN . `` The front-line CBP officers did not have access to the system that would 've informed them of a change in legal status . '' McCaul said it indicates `` disconnects '' and problems with information-sharing among Homeland Security agencies . Sen. Chuck Grassley , ranking member of the Senate Judiciary Committee , said Friday he also has concerns about gaps in the immigration system . `` It 's surprising that the administration is n't already verifying that any student coming into the country has a valid student visa , '' Grassley said . `` What 's more concerning is that nearly 12 years after the 9/11 terrorist attacks , we have n't fixed the problems with identifying visa overstays . '' Grassley sent a letter and list of questions Friday to Homeland Security Secretary Janet Napolitano , asking her about the apparent visa lapse with Tazhayakov and other possible loopholes . CNN 's Jake Tapper , Joe Johns and Ted Barrett contributed to this report .
NEW : Two U.S. lawmakers demand answers about their status . NEW : Rep. McCaul says it shows a `` serious hole '' in national security . DHS orders the verification of foreign student visas . Two friends of the Boston bombing suspect reportedly overstayed their visas .