Female DNA that was found on pieces of the pressure cooker bomb used in Boston could be misleading, authorities say.

Investigators stress that the pieces could have been contaminated with the DNA before the area was sealed off and doesn’t necessarily represent a third party who was involved in the bombings. They are, however, following all possible leads to determine whether a woman was in on the terrorist act.

Katherine Russell, Tamerlan Tsarnaev’s wife, is one of the people investigators are looking at as a potential owner of the DNA, although they stress that she might have handled the pressure cooker in the home she shared with her husband without having anything to do with the bombings. Russell has been cooperative with police and says she never knew what Tamerlan was planning because when he was home, she was at work.

As of right now, Dzhokhar Tsarnaev–the surviving suspect–has lawyers who are trying to avoid the death penalty for him. He has been cooperating with investigators while recovering from serious injuries in the hospital.

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