Earlier, CNN reported the FBI has interviewed "Misha," a man who allegedly had a radicalizing influence on suspected Boston Marathon bomber Tamerlan Tsarnaev.
The Journal, quoting U.S. officials briefed on the investigation, reported Monday it had yet to be determined whether a woman helped the two alleged bombers, brothers Tamerlan and Dzhokhar Tsarnaev.
The Journal said investigators collected DNA from Katherine Russell, Tamerlan Tsarnaev's widow, at her parents' home in Rhode Island where she has been staying since the April 15 bombing. Tsarnaev was killed in a shootout with police April 19.
Investigators also spoke with the man in Rhode Island after members of Tsarnaev's family blamed a "Misha" for influencing the alleged mastermind of the bombings, CNN reported.
"Misha," identified as Mikhail Allakhverdov by writer Christian Caryl, who said he interviewed him for a New York Review of Books article, denied encouraging a violent approach to Islam and insisted he was not Tsarnaev's teacher.
"He began telling me he cooperated with the FBI" and "handed over his computer" and cellphone, Caryl told CNN Monday, adding Allakhverdov insisted he had "nothing to do with [the] radicalization" of Tsarnaev.
The two bombs that exploded at the marathon finish like killed three people and injured more than 260. Dzhokhar Tsarnaev, 19, remains hospitalized with gunshot wounds and is charged with the crime.
The FBI is also investigating a possible link between Tamerlan Tsarnaev and three deaths on Sept. 11, 2011, police said.
FBI agents were working with prosecutors to interview family members and friends of the three victims in the unsolved Waltham, Mass., slayings, law enforcement authorities told ABC News Sunday.
Brendan Mess, 25; Raphael Teken, 37; and Erik Weissman, 31, had their throats slit. Last week, prosecutors confirmed to ABC News they were trying to determine whether Tsarnaev had any link to the Waltham slayings.
Family members of two victims said they had been contacted by the federal agency.