Landfill workers found a man's body in a pile of waste being deposited at the main Sonoma County landfill Wednesday, prompting a Sheriff's Office investigation.

Detectives responded early Wednesday afternoon to the central dump on Mecham Road near Cotati.

Workers made the discovery about 12:40 p.m. as they were unloading a new batch of garbage at the landfill, said Rick Downey, division manager for Republic Services, which manages the landfill.

The body was only visible from the chest up, Downey said. It was hard to tell how the man was dressed or what condition he was in, Downey said.

"Thank God we spotted him," Downey said. "If nobody knew he was gone, we might never have found him."

There were no obvious signs of foul play on the clothed, 39-year-old man. Detectives are withholding the man's name as they reach out to family. An autopsy is scheduled for Friday.

It was uncertain Wednesday exactly where the body originated, but based on the time it appeared at the landfill, it likely came from the Healdsburg transfer station, Downey said. That means it could have come from Windsor, Healdsburg or the surrounding rural area.

This isn't the first time a body has been found at a waste disposal site in Sonoma County. Last January, employees found a body at a waste transfer station in Petaluma. At the time, authorities said the man may have been sleeping in the dumpster to stay warm. Sheriff's Sgt. Shannon McAlvain could not say whether or not the man found Wednesday was homeless.

Downey said it's not uncommon for garbage truck drivers to find someone taking shelter in a dumpster. "It happens way more than you ever know," he said, adding that its something drivers "really have to be cautious of."

The landfill was closed for about three hours as sheriff's officials investigated. Other areas remained open for landfill customers to deposit their truckloads.

Staff Writer Randi Rossmann contributed to this report.