(NEW YORK) -- Female DNA was found on at least one of the bombs that exploded at the Boston Marathon on April 15, ABC News has learned, leaving open the possibility that the two suspects in the case might have had help constructing the device.
However, officials familiar with the probe cautioned that there could be multiple reasons why genetic material belonging to someone other than accused bombers Tamerlan and Dzhokhar Tsarnaev might have been on the bomb.
For instance, it could be the DNA of a merchant who unknowingly sold ingredients used to make the device, a stray hair or perhaps remains of victims from the blast.
Meanwhile, FBI agents on Monday visited the home of Katherine Russell's parents in Rhode Island. Russell is the widow of Tamerlan Tsarnaev, the older of the two brothers who died in a shootout with police in Watertown, Mass., on April 19.
Those familiar with the case said the agents wanted to collect DNA samples from Russell, who has been staying with her parents.
While Russell's attorney says she is "doing everything she can to assist with the investigation," it's believed investigators want to know if Russell's DNA matches what was found on one of the bombs.
According to a report in Tuesday's New York Times, an unidentified fingerprint was also found on a bomb fragment and the FBI is collecting samples from several people other than Russell in an effort to make a match.
As many as a dozen people are listed as persons of interest in the probe to determine whether the suspects had assistance, either before the twin blasts that killed three people and wounded more than 260, or during the days leading up to Tamerlan Tsarnaev's death and the capture of Dzhokhar Tsarnaev, who is recuperating from wounds at a federal prison medical facility outside of Boston.
Copyright 2013 ABC News Radio