One of three college students arrested in the Boston Marathon bombings case was allowed to return to the US from Kazakhstan in January despite not having a valid student visa.
The authorities charged the student - a friend and classmate of one of the men accused of setting off the pair of deadly explosions on April 15 - with helping to remove a laptop and backpack from the suspect's dormitory room after the attacks and before the FBI searched it.
The government acknowledged that US Customs and Border Protection was unaware that the student was no longer in college when he was let back into the US.
The disclosure was another instance of possible lapses by the government in the months before the bombings. The Obama administration earlier this week announced an internal review of how US intelligence agencies shared sensitive information and whether the government could have prevented the attack.
Federal authorities on Wednesday arrested three college friends of suspect Dzhokhar Tsarnaev, including Azamat Tazhayakov, a friend and classmate of Tsarnaev at the University of Massachusetts Dartmouth.
Tazhayakov left the US in December and returned on January 20. But in early January, his student visa status was terminated because he was academically dismissed from the university, a law enforcement official said.
The official said information about Tazhayakov's status was in the Homeland Security Department's Student and Exchange Visitor Information System, called SEVIS, when Tazhayakov arrived in New York in January.
DHS spokesman Peter Boogaard said that when Tazhayakov returned on January 20, Customs and Border Protection officials had not been notified that he was no longer a student.
Mr Boogaard said that DHS was reforming the visa system to ensure that CBP would have access to all relevant student visa information. "At the time of re-entry there was no derogatory information that suggested this individual posed a national security or public safety threat," he said.
Tazhayakov and another student from Kazakhstan, Dias Kadyrbayev, were detained last month on immigration charges. They were arrested on federal criminal charges of conspiracy to obstruct justice. Robel Phillipos, 19, was also arrested and charged with making false statements to federal law enforcement officials during a terrorism investigation.