Forensic analysis has uncovered the presence of female DNA on bomb shards recovered from the deadly terrorist attack at the Boston Marathon earlier this month. Unidentified U.S. officials tell the Wall Street Journal that investigators do not know to whom the DNA belonged, and they caution that the DNA does not necessarily mean another suspect was involved in the attack:

There could be multiple explanations for why genetic material from someone other than the two bombing suspects—Tamerlan Tsarnaev and his younger brother, Dzhokhar—could have been found on remnants of the exploded devices. It could have come, for example, from a store clerk who handled materials used in the bombs or a stray hair that ended up in the bomb.

Yesterday investigators searched the Rhode Island home of the parents of Katherine Russell, the widow of Tamerlan Tsarnaev. The Daily News reports that investigators "scoured" the home and left with evidence bags, including one marked “DNA samples.” Russell's lawyer has said that his client is fully cooperating with the investigation.

Meanwhile, in a "WORLD EXCLUSIVE" interview with The Sun, Tamerlan's ex-girlfriend, Nadine Ascencao, 24, says the former boxer tried to brainwash her into “hating America like he did” and beat her for dressing like a typical teen. She started dating him when she was 17, and says, “I went to his mosque a couple of times and even looked into converting to make him happy. I thought, ‘This is crazy’ — but I still did it for him."

On one occasion, Ascencao says Tamerlan assaulted her for wearing a tank top and shorts at a pool party. “He wouldn’t let me watch TV or listen to the radio," she tells the Sun. "He’d say, ‘TV is the project of Satan’ and claimed Satan sent us messages through commercial music... He hated my tight trousers and made me wear long skirts. Towards the end I was wearing a hijab."

There's still no substantive indication that the brothers had any outside help in allegedly carrying out the bombing, but Russian authorities say Tamerlan exchanged online messages with a Russian-born boxer named William Plotnikov, who fought with militants in the North Caucasus. They also say Tamerlan met several times with an alleged jihadist recruiter named Mansur Makhmud Nidal when he was in Dagestan's capital of Makhachkala last year.

Nidal was killed during a shootout with police last May, while Plotnikov was killed two months later during a raid in a village southwest of Makhachkala. Tamerlan returned to the U.S. shortly thereafter. Russian officials say there's no evidence that Plotnikov ever met with Tamerlan in person, but one tells the Journal, "He intended to join the fighters, but he lost his contacts. In the end he picked an easier enemy in Boston."