Female DNA found on Boston Marathon pressure-cooker bomb

WASHINGTON -- The FBI has found female DNA on at least one of the two homemade bombs detonated during the Boston Marathon on April 15, according to a law enforcement official.

The presence of genetic material does not necessarily mean a woman helped build the pressure-cooker bombs, said the official, who spoke on condition of anonymity because the investigation is ongoing.

The genetic material could have come from a woman who was in the room where the devices were built, or from a cashier at a store where one of the bomb parts was purchased, the official said.

The test results have prompted investigators to look more closely at women who may have had contact with the alleged bombers, Tamerlan Tsarnaev and his younger brother, Dzhokhar Tsarnaev. Investigators are collecting DNA samples from some women who were close to the pair to provide a comparison.

On Monday, investigators visited the Rhode Island home of the family of Katherine Russell, the widow of the elder brother, who was killed in a shootout with police on April 19. Dzhokhar Tsarnaev was wounded but captured, and faces federal charges of using a weapon of mass destruction.

The two remote-controlled bombs killed three people and injured more than 260.

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