Bomb DNA not a match for suspect's widow

Warwick Police Department via AP

This 2007 booking photo released by Warwick, R.I., police shows Katherine Russell, arrested on shoplifting charges there. Charges were later dismissed. Russell is the widow of Tamerlan Tsarnaev, a suspect in the Boston Marathon bombings.

By Pete Williams and Erin McClam, NBC News

DNA found on a fragment of one of the Boston Marathon bombs does not match DNA taken earlier this week from Katherine Russell, the widow of the dead suspect in the attack, but she remains under scrutiny, investigators told NBC News.

Investigators said they still have many questions for Russell because they believe the bombs were assembled at the home she shared with her husband, Tamerlan Tsarnaev, who was killed in a firefight with suburban Boston police April 19.

Russell converted to Islam in 2009, after meeting Tsarnaev in a nightclub, and married him in 2010. She said through her lawyer that his alleged involvement in the attack came as an absolute shock.

Investigators said earlier this week that a piece of one of the pressure-cooker bombs set off by the brothers had a womans DNA on it, and that they wanted to determine who else might have handled the bombs.

Federal agents with bomb-sniffing dogs searched in Dartmouth, Mass., on Friday after people living there said they heard loud booms a month ago. The surviving suspect, Dzhokhar Tsarnaev, was a student at the University of Massachusetts-Dartmouth.

John Sladewski / The Standard-Times via AP

Massachusetts State Police walk out of the woods of The Smith Neck Farm in Dartmouth, Mass., on Friday.

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Bomb DNA not a match for suspect's widow