(CNN) -- Blood found on the scene of a Michigan kidnapping belonged to the victim, police said Thursday.
Jessica Heeringa, 25, was abducted late last month from an Exxon station in Norton Shores, where she was working alone, sometime around 11 p.m., police have said.
Investigators found "suspicious substances" at the station and turned them in to the state's crime lab, which identified some of it as blood. A DNA analysis matched it to Heeringa, the Norton Shores Police Department said.
The amount of blood found was small, police said. Authorities notified the family of the findings.
Police have put a face with the description of a man suspected of kidnapping the gas station cashier.
He is a white male, about 6 feet tall, between 30 and 40 years old, with wavy hair parted in the middle. On Tuesday evening, police released a sketch of the suspect.
Police also are looking for a silver minivan -- possibly a Chrysler Town and Country -- that was seen at the gas station.
"We have one witness who placed that vehicle there and saw the driver. That's what we based that description on so far," Norton Shores Police Chief Daniel Shaw told CNN affiliate WOOD-TV.
Video from a nearby business showed the suspected minivan in the area around the time Heeringa went missing.
The video is blurry, the van is only seen for a few seconds, and neither a driver nor license plate can be seen.
"I wish I had the technology like you see on TV where you could blow it up and I could see the driver inside. But that doesn't exist for me," Shaw told WOOD. But it is something.
"It does give us some hope that we've got some accurate information out there to work with," he told the station.
How she disappeared
Heeringa was scheduled to close the Exxon station where she was working alone at 11:30 p.m. on April 26. But at 11:15, police got a 911 call that the station was unmanned.
"It's very suspicious why there's nobody here," the 911 caller says in a tape.
The way the station was left, police say, led them to believe somebody abducted Heeringa.
"Her purse and other belongings were undisturbed. In addition, the store's cash drawer was found out, and no money was missing," police said in a statement.
Heeringa is described as 5 feet 1 inches tall, weighing 110 pounds, with blond hair, blue eyes and wearing wire-rimmed glasses.
Heeringa's mother, Shelly Heeringa, has said that she suspects someone familiar with the gas station and possibly known to Jessica took her daughter.
"I think whoever did this had been in the gas station before and maybe Jessie knew him," Shelly Heeringa said.
"He probably lured her out by saying he needed help," she said. "Jessie would have helped anybody. And that was probably her downfall."
Lack of surveillance images
The station did not have security cameras, something that police said has hindered the investigation and that Shelly Heeringa said always troubled her.
"When I knew she was working there, when I knew (the store) had no security cameras, when she was going to be by herself, I expressed my concern about it all the time to her how worried I was," the mother said.
But those concerns apparently didn't trouble Jessica.
"She just thought she could handle everything," Shelly Heeringa said.
The mother also thanked the community of 22,500 on the shores of Lake Michigan for its support in the search for her daughter.
"So many people have been trying to help us find Jessie. It's just been wonderful," she said.
People with information that may help find Jessica Heeringa are asked to call Norton Shores police at 231-733-2691.