Boston Marathon bombing suspect Dzhokhar Tsarnaev has been moved to a prison medical facility as authorities continue to search for answers about the attack.
The U.S. Marshals Service said Friday that Tsarnaev was moved to the Federal Medical Center Devens, a Bureau of Prisons facility in the northeastern state of Massachusetts. He was transferred there from a Boston hospital where he had been receiving treatment for injuries sustained during his capture last week.
A spokesman did not give details about the condition of the 19-year-old, who officials say is recovering from a neck wound.
Tsarnaev's brother and alleged co-conspirator, 26-year-old Tamerlan Tsarnaev, died in a confrontation with police last week.
Also Friday, FBI agents searched a landfill near the campus of the University of Massachusetts Dartmouth, where Dzhokhar Tsarnaev was a student. Officials did not say what investigators were looking for.
In Washington, lawmakers said that authorities are trying to determine whether or not the brothers' mother was involved in the radicalization of her two sons. The top Democrat on the House Intelligence Committee, Dutch Ruppersberger, said she is a "person of interest."
The Associated Press reported Friday that the bombing suspects' mother, Zubeidat Tsarnaeva, had been added to a federal terrorism database about 18 months before the Boston attack.
In Russia, Tsarnaeva and her former husband, Anzor, said Thursday their sons did not carry out the Boston attack that killed three people and injured more than 250 others.
In a news conference in Makhachkala, the parents said their sons were framed, and the mother accused U.S. authorities of needlessly killing Tamerlan.
"What have you done with my son? He was alive. Why did they need to kill him? Why didn't they send him to, you know, Guantanamo or wherever? Why did they kill him? Why? Why did they have to kill him? They got him alive, right? He was in their hands,'' she said.
Tsarnaeva said she would not accept that her sons had planted the bombs.
Dzhokhar Tsarnaev faces a charge of using a weapon of mass destruction, which carries a possible death sentence if he is convicted.
New York officials say the suspects were devising a plan to attack Times Square as they were running from authorities. New York Police Chief Ray Kelly said Dzhokhar told investigators they planned to drive to New York to set off their remaining explosives.
He said the plan fell apart when they realized the vehicle they had hijacked was running low on gas. When they stopped to refuel, the driver of the car escaped, and alerted police to their location.
New York Mayor Michael Bloomberg said the incident shows that New York, which was hit by terrorist attacks in 2001 that killed nearly 3,000 people, remains an inviting target.
"The fact is New York City remains a prime target for those who hate America and want to kill Americans," said Bloomberg.
U.S. officials are continuing to examine whether the Boston Marathon attack could have been prevented, as warning signs emerged that Tamerlan was turning toward extremism.
Senator Lindsey Graham said he believes Boston is becoming "a case study in system failure" by U.S. intelligence agencies.
“We need to understand that Bin Laden may be dead, but the war against radical Islam is very much alive. Radical Islam is on the march and we need to up our game,” said Graham.
Authorities say Tamerlan Tsarnaev was placed on a U.S. counter-terrorism list in late 2011.
The officials say the CIA asked that his name be placed on the list after the agency was contacted by the Russian government with its concerns that he had become a radical Islamist.
Moscow also issued a similar warning on him to the FBI earlier in 2011. Officials say the agency launched an investigation, but eventually concluded he posed no threat.
U.S. lawmakers have raised concerns about information sharing between U.S. law enforcement and intelligence agencies in the aftermath of the Boston Marathon attack. Authorities will brief the full U.S. Senate on the investigation into the bombing.
Several months after he first came to the attention of U.S. federal agents, Tamerlan Tsarnaev left the U.S. in January 2012 for a six-month visit to Russia.
U.S. investigators questioned the suspects' parents in the Russian republic of Dagestan to try to determine if Tamerlan had contacts with Islamic extremists. The family is originally from Chechnya, where Muslim insurgents have for decades been engaged in a bloody conflict with Russia.