HAYWARD -- Police on Monday were investigating what killed a man whose body was found in a marshy area along the Hayward shoreline near the Union City border.
The body was discovered about 12:30 p.m. Friday by a California Department of Fish and Wildlife biologist in a ravine just south of the San Mateo Bridge, said Sgt. Ken Forkus.
The biologist told police she was working on Eden Landing Ecology Reserve monitoring plant life when she noticed the man lying face down in the mud, Forkus said.
Officers responded and found the unresponsive man shirtless, lying in a tributary that runs into the Bay.
Emergency medical personnel pronounced him dead at the scene.
Although police do not yet know how long he'd been dead, the man's body was in a state of decomposition.
An autopsy was performed on Monday, Forkus said, but authorities have not yet identified the victim.
"We don't know if it was suicide or natural causes at this point or if foul play is suspected," Forkus said.
Anyone with information about the case is asked to call police at 510-293-7000 or the anonymous tip line at 510-293-7197.
Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.