NORTON SHORES, Mich. -

One month after Jessica Heeringa disappeared from a west Michigan gas station, police believe the missing mother is still alive.

Police have sorted through more than 2,000 tips, but have not found the 25-year-old.

Norton Shores police Chief Dan Shaw said Friday that while the tips "have slowed down somewhat," some of them are high-priority tips that are worth checking out.

Heeringa disappeared April 26 before she was set to close the station in Norton Shores, near Muskegon. Police say there's no indication of a robbery. A task force is investigating.

Norton Shores Exxon

Police have released a description of a silver minivan and a man seen in the area.

Surveillance in Heeringa case

Tests done on droplets found at the gas station have come back positive for Heeringa's blood.

Police have released a description and composite sketch 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.