(CNN)- New details are surfacing in the Boston Marathon bombings. Investigators say they have found female DNA on a fragment of the pressure cooker bombs used in the attack.
On Monday, they searched the family home of Tamerlan Tsarnaev's widow, Katherine Russell. Tsarnaev was killed during a firefight with police April 19 after he and his brother Dzhokhar carjacked a vehicle.
Sources warn that even if Russell's DNA is found on the cooker, it doesn't prove that she was involved in the preparation of the bomb. Russell says she was unaware of her husband's plan.