One law enforcement source said earlier this was based on what surviving suspect Dzhokhar Tsarnaev, 19, told investigators in a Boston hospital. He is recovering from gunshot wounds in Beth Israel Deaconess Medical Center, where he was formally charged on Monday with crimes that could carry the death penalty.
Tsarnaev's attorney, Miriam Conrad, declined to comment on Thursday on whether her wounded client was still talking with investigators.
Meanwhile, the father of the brothers said he planned to travel to the United States from Russia to bury his older son, Tamerlan Tsarnaev, who was killed in a police shootout.
"I am going to the United States. I want to say that I am going there to see my son, to bury the older one. I don't have any bad intentions. I don't plan to blow up anything," Anzor Tsarnaev told reporters in Makhachkala, the capital of Russia's Dagestan region.
The bombing killed three people and injured 264 others.
Near Washington, the focus remained on intelligence leading up to the Boston Marathon bombing. Tamerlan Tsarnaev had been on a federal database of potential terrorism suspects and that the United States had twice been warned about him by Russian authorities. Congressional testimony earlier in the week had focused on whether the Federal Bureau of Investigation made mistakes in tracking the ethnic Chechen.
"We're in the post-event witch hunt phase, which is predictable," said James Clapper, Director of National Intelligence, at a conference in Crystal City, Virginia. "I think it would be a real good idea to not hyperventilate for a while now until we actually get all the facts."
Anzor's former wife, Zubeidat Tsarnaeva, angrily denied that her son had any role in the attack and criticized police for shooting her 26-year-old son while apprehending him.
Tsarnaeva does not plan to accompany her former husband on his trip. One factor that may have influenced Zubeidat Tsarnaeva's decision not to travel with her former husband is an outstanding arrest warrant in Massachusetts.
A warrant for Zubeidat Tsarnaeva's arrest was issued on October 25 after she failed to make a court appearance on shoplifting-related charges, according to Natick District Court Clerk Brian Kearney.
Tsarnaeva was arrested in June at a Lord & Taylor department store on suspicion of shoplifting $1,624 worth of women's dresses, according to the Natick Police Department.
Tamerlan Tsarnaev's widow, 24-year-old Katherine Russell, also has a criminal record. In 2007, shortly after graduating from high school, she was arrested for stealing five items valued at $67.00 from an Old Navy in Warwick, Rhode Island.
Russell's lawyer, Amato DeLuca, said earlier this week that his client knew nothing about the Tsarnaev brothers' activities.
The U.S. Marshals Service, which is responsible for holding and transporting suspects outside of prison, declined to comment on whether or when Dzhokhar Tsarnaev might be moved from the hospital.
"It is our policy not to comment on prisoner movements until they have been completed," said spokeswoman Lynzey Donahue. "We do ensure that prisoners in our custody receive medical services in a secure environment."
Bombs were detonated by remote used for toy cars
The two bombs that went off at the Boston Marathon, killing three people and wounding 264, were detonated with the kind of remote device used to control a toy car, U.S. investigators told a House of Representatives panel on Wednesday.
"It was a remote control for toy cars," U.S. Rep. Dutch Ruppersberger, the top Democrat on the House Intelligence Committee, told reporters after officials from the Department of Homeland Security, FBI and National Center for Counterterrorism briefed the committee.
"Which says to me, and brother number two has said, they got the information on how to build the bomb from Inspire magazine," Ruppersberger added.
Inspire was created by the American-Yemeni preacher Anwar al-Awlaki, a leader of al Qaeda's affiliate in Yemen who was killed in a U.S. drone strike.
Ruppersberger said the article on bomb-building in Inspire was headlined: "How to build a bomb in your mom's kitchen."