Updated

Police in Michigan are trying to figure out how an old Buick with human remains inside ended up at the bottom of a pond, and how long it's been there.

The 1973 Buick Electra 225 was discovered tuesday in a man-made pond next to a highway in Buena Vista Township by divers contracted by the Michigan Department of Transportation to clear barrels from it, MLive.com reports.

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In this Aug. 15, 2017 photo, Michigan State Police Forensic Laboratory detectives investigate the scene where a car containing a body was discovered submerged in a pond in Buena Vista Township, Mich. The discovery of the Buick sedan was made by workers removing barrels from the pond. (Jacob Hamilton/The Bay City Times via AP) (AP)

Township police Detective Sgt. Greg Klecker said the car has an older license plate, but won't reveal further details until a forensic report the vehicle and the remains is completed.

The pond is on state property roughly 80 miles northwest of Detroit. Michigan Department of Transportation spokeswoman Jocelyn Hall says the barrels were being removed because someone reported they were in the pond. The contents weren't known.

The Associated Press contributed to this report