U.S. media outlets quote unnamed law enforcement officials as saying the bombs used in the deadly Boston Marathon attack were made in the apartment that elder suspect Tamerlan Tsarnaev shared with his wife and child.
Tamerlan was killed in a shootout with police April 19 just days after the attack, which killed three people and wounded more than 260. Officials say he and his younger brother Dzhokar set off the two bombs.
This latest news raises questions about how much Tamerlan's widow might have known about the attack. Investigators have been questioning Katherine Russell as they try to determine how the suspects built their bombs and whether they had help. They have also been questioning Dzhokar, who was captured.
Officials have said the Tsarnaev brothers were originally planning attacks for July 4 - U.S. Independence Day - and had considered suicide bombings. Dzhokhar reportedly told the FBI that the brothers moved up their attack plans to April 15 because they finished building their bombs sooner than expected.
Both April 15 (Patriots' Day) and July 4 (Independence Day) are occasions for large patriotic celebrations in Boston.
Tamerlan Tsarnaev's family members claimed his remains on Thursday after his widow issued a statement saying she would relinquish her rights to his body to them.
There were no details on where Tamerlan's body was taken. Dzhokhar is in a prison hospital, recovering from gunshot wounds.
The New York Times reports Dzhokhar also told authorities that he and his brother viewed online videos of the sermons of radical American cleric Anwar al-Awlaki, who was killed in September 2011 by a U.S. drone strike. There was no indication that the brothers communicated directly with Awlaki.
Meanwhile, Kazakhstan says it is cooperating with U.S. authorities after two Kazakh nationals were arrested for allegedly obstructing the bombing investigation. The two Kazakhs and an American allegedly helped Dzhokhar Tsarnaev destroy evidence. They are not accused of direct involvement in the bombing. The three young men attended college with Dzhokhar.