GROVE, Okla. (AP) — Authorities in northeast Oklahoma are investigating the remains of a man found in Grand Lake.

Grand River Dam Authority Police Chief Brian Edwards says a person walking nearby discovered the body on Tuesday west of Sailboat Bridge, less than a mile southeast of Grove. Police are unsure how long the body had been in the lake before it was discovered.

Authorities haven't officially identified the body yet, but believe the remains are that of a white man between 25 and 30 years old.

Edwards says the investigation is in preliminary stages and that the Oklahoma Bureau of Investigation has been called to assist.

Authorities say the state Medical Examiner's Office is expected to conduct an autopsy on the body to determine the cause of death.