Female DNA has been found on at least one of the Boston Marathon bombs, but investigators have not determined whose it is or whether it suggests a woman helped the two brothers blamed for the deadly April 15 blasts, The Wall Street Journal reports and USA Today has confirmed. Officials familiar with the case cautioned that there exist several explanations for why the DNA of someone other than the two bombing suspects could have been found on remnants of the exploded devices. The genetic material may have come, for example, from a store clerk who handled bomb materials, a stray hair that ended up in the bomb, or perhaps from a marathon bystander. Finally, NPR reports the man known as ‘Misha’ – whom relatives of the elder Tsaernev allege radicalized him – denies he was Tamerlan’s teacher, but covers his bases, adding: “If I had been his teacher, I would have made sure he never did anything like this.”