The Homeland Security Department ordered its border agents "effective immediately" to verify that every international student who arrives in the US 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 from a senior official at US Customs and Border Protection, David J Murphy, was circulated Thursday and came 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 US in January without a valid student visa.The student visa for Azamat Tazhayakov had been terminated when he arrived in New York on January 20. But the border agent in the airport did not have access to the information about it in the Homeland Security Department's Student and Exchange Visitor Information System (SEVIS).

A spokesman for the department, Peter Boogaard, said earlier this week that the government was working to fix the problem, which allowed Tazhayakov to be admitted into the country when he returned to the US.Tazhayakov and a second Kazakh student were arrested this week on federal charges of obstruction of justice. They were accused of helping to get rid of a backpack containing fireworks owned by bombing suspect Dzhokhar Tsarnaev. A third student was also arrested and accused of lying to authorities.