A woman's DNA has been found on at least one of the explosive devices used in the Boston bombings, adding a new dimension to the probe into the terror attack that killed three people and wounded over 200 others.
The findings, reported by the United States media, have raised the possibility of involvement of a woman in the Boston Marathon twin blasts, which is blamed on two Chechen-origin brothers.
The US authorities have arrested Dzhokhar Tsarnaev, 19, on charges of using a weapon of mass destruction, while his brother Tamerlan, 19, was shot dead by the police.
"Investigators have found female DNA on at least one of the bombs used in the Boston Marathon attacks, though they haven't determined whose DNA it is or whether its presence means a woman helped the two brothers suspected in the bombings," The Wall Street Journal said quoting US officials.
"No one should expect that the investigation is over," an investigator was quoted as saying by Fox News, according to which this raises the possibility of involvement of a woman.
Meanwhile, federal investigating authorities on Monday searched the Rhode Island home of parents of Katherine Russell, the widow of Tamerlan, and the nearby family of a man identified as his mysterious mentor.
Federal authorities took a sample of Russell's DNA on Monday in Rhode Island, where she has been staying with her parents, The New York Times reported.
Federal agents are looking into possible links between dead Tamerlan and a Canadian boxer-turned-jihadist killed by Russian troops in 2012, the CNN reported.
"William Plotnikov and six others died in a firefight with Russian forces in the southwestern republic of Dagestan in July 2012, while Tsarnaev was visiting the region," it said.
"Twenty-three-year-old Plotnikov had been born in Russia, but his family moved to Canada when he was a teenager," CNN reported.
Plotnikov's body was prepared for burial by a local imam on July 14. Tamerlan flew out of Dagestan two days later, arriving in New York on July 17. Since 2000, Dagestan has witnessed clashes between Islamists and security forces that has claimed hundreds of lives. Investigators are looking into the possibility he left because of Plotnikov's death, CNN said quoting its unnamed source.