May 8, 2013 — -- Police investigating the disappearance of Jessica Heeringa, the Michigan woman abducted in late April during her shift at a gas station, said that the suspicious substance found at the scene where she vanished was her blood.
"The substance has been confirmed as blood," police said in a statement released today. "Based on a subsequent DNA analysis, the blood has been confirmed to be from Jessica Lynn Heeringa."
Police said that there was only a small amount of blood located at the Norton Shores, Mich., Exxon gas station where Heeringa was working at a late shift. The 25-year-old mother of one was within moments of closing the station when she vanished.
Heeringa's family has been notified that her blood was found at the scene, police said.
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On May 2, authorities released a surveillance video showing a van believed connected to Heeringa's disappearance. Prior to the blood being identified as hers, there appeared to be no signs of struggle at the service station, and Heeringa's purse and keys were found inside the store. No money had been removed from the register, leading police to believe that the woman knew her abductor.
An employee at a store adjacent to the gas station where Heeringa worked said he noticed a man in a minivan talking to her, but didn't think much of the interaction until he learned she had been abducted.
"It just seemed to me that this was just another guy hitting on her, or whatever, because she was an attractive girl," Christian VanAntwerpen said of the April 26 incident. "It was just an afterthought I almost didn't think about mentioning. [But] I thought it was my responsibility to say something about it."
VanAntwerpen said he watched a man in a silver minivan approach Heeringa when she was at a gas pump preparing to close the station, where she had been working alone on the late shift.
"He was just like, 'Hey, what are you doing over here? Aren't you supposed to be inside?' Just kind of being real flirty, weird about it," he said. "It was just bizarre that he seemed to be actively looking for her, like he knew her and then had this attitude that he wanted to have a conversation with her and then conduct business, and that is what seemed really out of place to me."
Police have released a composite sketch of the minivan driver, a person of interest described as a white male, six feet tall with a medium to heavy build.
Investigators have interviewed and cleared several people of interest, police said, including Heeringa's fiance, with whom she has a 3-year-old son.
ABC News' Alex Perez and Matthew Jaffe contributed to this report.