WASHINGTON (AP) — The Homeland Security Department ordered border agents to verify that every international student who arrives in the U.S. has a valid student visa, according to an internal memorandum obtained Friday by The Associated Press. The new procedure is the government’s first security change directly related to the Boston bombings.

The order, which is effective immediately, came from a senior official at U.S. Customs and Border Protection, David J. Murphy. It was circulated Thursday, one day after the Obama administration acknowledged that a student from Kazakhstan accused of hiding evidence for one of the Boston bombing suspects was allowed to return to the U.S. in January without a valid student visa.