Customs officials are being ordered "effective immediately" to verify that every foreign student arriving in the US has a valid student visa.
It is the first security change by the US government directly related to the Boston bombings.
According to an internal memorandum obtained by The Associated Press, the Homeland Security Department says every international student holding a non-immigrant student visa must have their status verified before being allowed into the US.
The order comes 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.
Azamat Tazhayakov's terminated visa status was in the Student and Exchange Visitor Information System, called SEVIS.
