US security officials are to face questions in Congress over whether they mishandled information about Boston bombing suspect Tamerlan Tsarnaev.
They will brief the Senate Intelligence Committee in a closed hearing, after some US lawmakers accused the FBI of failing to act on Russian concerns.
Tsarnaev was questioned in 2011 amid claims he had adopted radical Islam.
He was killed in a manhunt after the attack but his wounded brother Dzhokhar has been charged over the bombings.
The Beth Israel Deaconess hospital in Massachusetts said at noon on Tuesday that the surviving brother’s condition had improved from “serious” to “fair”, according to the US Attorney’s Office in Boston.
Federal prosecutors have charged him with using a weapon of mass destruction and malicious destruction of property resulting in death. He could be sentenced to death if convicted on either count.
Anonymous officials have told US media that 19-year-old Dzhokhar Tsarnaev said he and his brother had planned the attack themselves without help from foreign militants.
The officials say his written answers from his hospital bed to investigators’ questions lead them to believe that the pair were motivated by jihadist ideology and that they devised the bombings using the internet.
However, the sources also said the interviews were preliminary and they must verify the defendant’s responses.
Lawyers for Katherine Russell, the widow of 26-year-old Tamerlan Tsarnaev, said that their client was doing everything she could to assist authorities.
She is “trying to come to terms with these events”, her lawyers said in a statement on Tuesday, without saying whether she had been questioned by investigators.
“The report of involvement by her husband and brother-in-law came as an absolute shock to them all.”
Both Tsarnaev brothers had origins in the troubled, predominantly Muslim republic of Chechnya in southern Russia. They had been living in the US for about a decade at the time of the attack.
