NORTON SHORES, Mich. – Tuesday Norton Shores police released a sketch of a man they are searching for in connection to Jessica Heeringa's disappearance.
Police say the man in the sketch is a person of interest
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Heeringa went missing from a Michigan gas station Friday night after police believe someone grabbed the 25-year-old mother.
Heeringa was scheduled to close the Exxon station where she was working alone at 11:30 p.m. Friday.
It wasn't until after she was gone that a customer realized something was wrong inside the store. 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 police released Monday.
Listen: Driver finds gas station unattended, calls 911
Norton Shores, Mich., Police Chief Daniel Shaw said that by Tuesday morning authorities had gotten 150 tips in the Heeringa case, but nothing conclusive.
"A lot of interesting tips that we can follow up on. Whether or not they're solid, it's hard to say because we have so little to work on with physical evidence. We're just grasping at straws. ... We're grasping for straws with whatever we can find at the scene," Shaw told CNN affiliate WOOD.
Shaw said a DNA sample was found at the gas station, but he could not tie it to Heeringa's disappearance, WOOD reported. That sample is being tested.
Surveillance video from a Norton Shores bar could help in the case. In the video, a gray minivan is seen driving past the bar and police are now searching for the driver.
Watch: Surveillance video from bar of silver van
Worried family and friends spent Monday passing out flyers. "When I see so many people come here and say, 'Oh, I knew Jessica,' or even knew her just from work, take the time to come over and ask for help, I think it's a sign or what a unique young lady she was," said Diane Homrich, Heeringa's grandmother.
Police believe Heeringa may have known her abductor because there is no sign of a struggle. They have already ruled out several suspects.