This image taken from surveillance video provided by the Boston Regional Intelligence Center shows Boston Marathon bombing suspect Dzhokhar Tsarnaev at a Bank of America ATM in Watertown, Mass. at 11:18 p.m. on April 18, 2013. The next day, police intercepted Dzhokhar and his 26-year-old brother Tamerlan in a blazing gunbattle that the elder brother dead. AP Photo/Boston Regional Intelligence Center BOSTON (AP) - Boston Marathon 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 deadly plot was pulled off and searched for evidence Friday in a landfill near the college he attended. Tsarnaev, 19, was taken from Beth Israel Deaconess Medical Center, where he was recovering from a throat wound and other injuries suffered during an attempt to elude police last week, and he was transferred to the Federal Medical Center Devens, about 40 miles from Boston, the U.S. Marshals Service said. The facility, at a former Army base, treats federal prisoners. "It's where he should be; he doesn't need to be here anymore," said Beth Israel patient Linda Zamansky, who thought his absence could reduce stress on bombing victims who have been recovering at the hospital under tight security. The FBI's investigation of the April 15 bombing has turned from identification and apprehension of suspects to piecing together details of the plot, including how long the planning took, 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 the condition of anonymity on Friday that the FBI was gathering evidence regarding "everything imaginable." FBI agents picked through a landfill near the University of Massachusetts Dartmouth, where Tsarnaev was a sophomore. An aerial photo in Friday's Boston Globe showed a line of more than 20 investigators, all dressed in white overalls and yellow boots, picking over the garbage with shovels or rakes. 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, 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. Previously U.S. officials had said only that the FBI investigated Tamerlan Tsarnaev. "It's all lies and hypocrisy," she said from Dagestan. 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. Meanwhile, New York's police commissioner said the FBI was too slow to inform the city that the Boston Marathon suspects had been planning to bomb Times Square days after the attack at the race. Federal investigators learned about the short-lived scheme from a hospitalized Dzhokhar Tsarnaev during a bedside interrogation that began Sunday night and extended into Monday morning, officials said. The information didn't reach the New York Police Department until Wednesday night. "We did express our concerns over the lag," said police Commissioner Raymond Kelly, who with Mayor Michael Bloomberg had announced the findings on Thursday. The FBI had no comment Friday. Contributing to this report were Associated Press writers Rodrique Ngowi in Boston, Colleen Long in New York and Pete Yost and Julie Pace in Washington.