BOSTON - With the Boston marathon bombing suspect in a prison hospital, investigators are pushing forward in the U.S. and abroad to piece together the myriad details of a plot that killed three people and injured more than 260.

FBI agents have wrapped up a two-day search at a landfill near the University of Massachusetts Dartmouth, where 19-year-old suspect Dzhokhar Tsarnaev was a sophomore. FBI spokeswoman Laura Eimiller wouldn't say what investigators were looking for or whether they recovered anything from the landfill before the search ended Friday.

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."

Meanwhile, U.S. officials said the bombing suspects' mother had been added to a federal terrorism database about 18 months before the April 15 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.

Russian authorities secretly recorded a telephone conversation in 2011 in which one of the Boston bombing suspects vaguely discussed jihad with his mother, officials said Saturday, days after the U.S. government finally received details about the call.

In another conversation, the mother of now-dead bombing suspect Tamerlan Tsarnaev was recorded talking to someone in southern Russia who is under FBI investigation in an unrelated case, officials said.

The conversations are significant because, had they been revealed earlier, they might have been enough evidence for the FBI to initiate a more thorough investigation of the Tsarnaev family.

Dzhokhar Tsarnaev is charged with joining with his older brother, Tamerlan Tsarnaev, 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 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 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.

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, Mass., in 2012.

Earlier this week, she said she has been assured by lawyers that she would not be arrested if she traveled to the U.S., but she said she was still deciding whether to go. The suspects' father, Anzor Tsarnaev, said that he would leave Russia soon for the United States to visit one son and lay the other to rest.

A team of investigators from the U.S. Embassy in Moscow questioned both parents in Russia this week.

Late this week, Dzhohkar Tsarnaev 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, and 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.

Two college buddies of his - Azamat Tazhayakov and Dias Kadyrbayev - have been interviewed at length, twice, by FBI agents and have cooperated fully, said Kadyrbayev's lawyer, Robert Stahl, a former federal prosecutor.

They were detained April 20 after being questioned in connection with the attacks, but are not suspects, Stahl said. They are being detained at a county jail in Boston for violating their student visas by not regularly attending classes, he said.

The two, both students from Kazakhstan, had nothing to do with the attack and had seen no hints that their friend harbored any violent or terrorist sympathies, Stahl said.

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.

The FBI had no comment Friday.