The FBI has confirmed one of the bombs that killed three in the Boston bombing bore female DNA.
According to a law enforcement official who spoke to the LA Times and wished to remain anonymous, a fragment of one of the pressure-cooker, homemade bombs had been handled by a female at some point.
This genetic material does not mean a woman helped build the bombs-the pressure-cookers might have been brushed by a woman in the room, or by the hand of a salesperson at a store where a part was purchased.
As a result of this new finding, investigators are looking more closely at female relatives and friends who potentially had contact with the suspected bombers, Tamerlan Tsarnaev and his younger brother, Dzhokhar Tsarnaev.
FBI officers visited Tamerlan's widow Katherine Russell's home in Rhode Island Monday to collect a DNA sample.
Russell is not a suspect and has not been charged, but was close to Tamerlan for some time, and therefore must be investigated.
Investigators will take her sample and examine the results against the piece of metal that flew off when the bomb detonated.
FBI agents were seen leaving her family's house in North Kingstown with evidence, including a plastic bag marked, "DNA Samples".
Russell has said her husband's alleged bombing the Boston Marathon "shocked" her and members of her family.
Younger brother Dzhokhar, who survived the attacks, could have some of the answers, but investigators have reportedly not spoken with him since he was found hiding in a boat outside Watertown, Massachusetts.
Former CIA agent Robert Baer spoke to CNN about the detailed design of the pressure-cookers, and that their construction could require another set of hands.
"And I have seen multiple reports...that police are looking at this as a sophisticated device...If that's the case, there's a master bomber out there," Baer said.