Azamat Tazhayakov and Dias Kadyrbayev were jailed by immigration authorities the day after Tsarnaev's capture. Kadyrbayev's lawyer, former federal prosecutor Robert Stahl, said the pair, who had partied with Tsarnaev and other students at an off-campus apartment, had nothing to do with the attack and had no idea their friend harbored any violent thoughts.
"These kids are just as shocked and horrified about what happened as everyone else," Stahl said. He said they are being held for violating their student visas by not regularly attending classes and want to return to Kazakhstan as soon as possible.
U.S. officials, meanwhile, said that the bombing suspects' mother had been added to a federal terrorism database about 18 months before the deadly attack — a disclosure that deepens the mystery around the Tsarnaev family and marks the first time American authorities have acknowledged that Zubeidat Tsarnaeva was under investigation before the tragedy.
The news is certain to fuel questions about whether President Barack Obama's administration missed opportunities to thwart the marathon bombing, which killed three people and wounded more than 260.
Tsarnaev is charged with joining with his older brother, now dead, in setting off the shrapnel-packed pressure-cooker bombs. The brothers are ethnic Chechens from Russia who came to the United States about a decade ago with their parents. Investigators have said it appears that the brothers were angry about the U.S. wars in Afghanistan and Iraq.
Two government officials, speaking on condition of anonymity because they were not authorized to speak publicly about the investigation, said the CIA had Zubeidat Tsarnaeva's name added to the terror database along with that of her son Tamerlan Tsarnaev after Russia contacted the agency in 2011 with concerns that the two were religious militants.
About six months earlier, the FBI investigated mother and son, also at Russia's request, one of the officials said. The FBI found no ties to terrorism. Previously U.S. officials had said only that the FBI investigated Tamerlan Tsarnaev.