Traces of female DNA have been detected on at least one of the bombs used in the Boston terror attacks, the Wall Street Journal reports.
U.S. officials familiar with the situation say investigators have not yet determined who the DNA belongs to or whether that person was formally involved in making the bombs.
“The officials familiar with the case cautioned that there could be multiple explanations for why the DNA of someone other than the two bombing suspects—Tamerlan Tsarnaev and his younger brother, Dzhokhar—could have been found on remnants of the exploded devices,” the WSJ reports.
“The genetic material 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,” the report adds.
FBI agents were seen Monday leaving the home of Katherine Russell, the widow of Tamerlan Tsarnaev. The oldest Tsarnaev was killed in a shootout with police on April 15.
The WSJ provides more details:
Ms. Russell has been staying with her parents since the bombings, and FBI agents have been seen posted outside the home since her late husband was identified as one of the bombers. Her lawyer has said she is "doing everything she can to assist with the investigation."
One official familiar with the case said agents went to the house Monday to collect a DNA sample from Ms. Russell, the culmination of days of negotiations. FBI officials also have been negotiating with Ms. Russell's attorney in recent days to get fuller access to question her, the officials familiar with the case said. The officials briefed on the investigation said the DNA request was needed to determine whether it matched the DNA found on the bomb remnants.
Sources familiar with the investigation say Ms. Russell is one of about a half-dozen suspects authorities are scrutinizing to see if they were involved in helping carry out the terrorist attacks.
“Investigators have no evidence that any of the associates had knowledge of the bombing plot, and they believe that if anyone helped to dispose of evidence—a point that remains uncertain—it may have been unwitting, according to officials briefed on the investigation,” the WSJ adds.
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