By Melissa Gray, CNN
(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Tsarnaev, who are now charged in connection with the attack, may have been in the country on student visas that were no longer valid.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.