RAPID CITY, S.D. (KELO) — Police in Rapid City are working to identify a man found dead in a street water drainage tunnel.

Rapid City Police say that around 11:30 on Sunday, they were called to a street water drainage tunnel near East Boulevard and Omaha Street for a report of a dead man.

Authorities located the body behind a gated water runoff tunnel. Police say there were no signs of obvious trauma, but an autopsy is underway to determine the cause of death.