Boston Marathon bombing suspect Dzhokhar Tsarnaev has told investigators his brother's wife played no role in the planning or execution of the plot, according to a federal law enforcement source.
Despite that claim, investigators are continuing to scrutinize Katherine Russell to determine whether she broke any laws in connection with the case, the source said.
Russell spoke with her husband after his photo was released as one of the bombing suspects, but she did not notify authorities at the time, the source said.
Russell "plans to continue to meet with investigators, part of a series of meetings over many hours where she has answered questions," Russell's lawyers said in a statement issued Wednesday.
The attorneys also announced the addition of another lawyer, Joshua Dratel, of New York City, to their legal team.
Dratel has handled previous cases involving terrorism.
The addition of Dratel will help ensure "that Katie can assist in the ongoing investigation in the most constructive way possible," the statement said.
Meanwhile, federal agents continue to pursue leads in the investigation into what motivated the Tsarnaev brothers to carry out the bombings, which killed three people and injured more than 260, and whether they had help.
One focus of the investigation: an attempt to trace the gun allegedly fired by Tamerlan Tsarnaev during an April 19 shootout with police, the source said.
Their goal is to trace the gun back to its original owner and in turn learn when, where, how and from whom Tsarnaev got the gun, the source said.
Authorities allege the two brothers carried out the April 15 bombings near the race's finish line, using pressure cookers packed with explosives, nails, ball bearings and metal shards.
Tamerlan Tsarnaev died following a gun battle with police, and authorities captured Dzhokhar Tsarnaev after a massive manhunt following his escape from the same encounter.
The younger brother is now in a prison hospital, facing charges that could bring the death penalty.