BOSTON - Bombing suspect Dzhohkar Tsarnaev was moved from a hospital to a federal prison medical center while FBI agents shifted the focus of their investigation to how the plot was executed and searched for evidence Friday in a landfill near the college he attended.
Tsarnaev, 19, was transferred from Beth Israel Deaconess Medical Center, where he was recovering from injuries suffered while trying to elude police last week, to the Federal Medical Center Devens, about 40 miles from Boston, the U.S. Marshals Service said.
The FBI's investigation of the April 15 bombing has turned to piecing together details of the plot, including how long it was planned, how it was carried out and whether anyone else knew or was involved.
A federal law enforcement official not authorized to speak on the record about the investigation told The Associated Press on Friday that the FBI was gathering evidence regarding "everything imaginable."
FBI agents sifted through a landfill near the University of Massachusetts Dartmouth, where Tsarnaev was a sophomore. FBI spokesman Jim Martin would not say what investigators were looking for.
Investigators also have continued to interview people who were close to Tsarnaev, including two young men from Kazakhstan who were students with him at UMass Dartmouth.
Azamat Tazhayakov and Dias Kadyrbayev were jailed by immigration authorities the day after Tsarnaev's capture. Kadyrbayev's lawyer, 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, Zubeidat Tsarnaeva, 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.
The news is certain to fuel questions about whether President Obama's administration missed opportunities to thwart the marathon bombing, which killed three people and wounded more than 260.
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.
In an interview from Russia, Tsarnaeva denied any links to terrorism on Friday.
"It's all lies and hypocrisy," she said from Dagestan. "I'm sick and tired of all this nonsense that they make up about me and my children. … I've never been mixed up in any criminal intentions, especially any linked to terrorism."
Tsarnaeva faces shoplifting charges in the U.S. over the theft of more than $1,624 worth of women's clothing from a Lord & Taylor department store in Natick in 2012.