The body of a Portland man was found in a sinkhole partly filled with water in his backyard after a friend called police to say she hadn't heard from him, authorities said.

PORTLAND — The body of a Portland man was found in a sinkhole partly filled with water in his backyard after a friend called police to say she hadn't heard from him, authorities said.

Michael Zerwas, 57, died of a combination of hypothermia and drowning but survived the initial fall into the hole, according to Dr. Karin Gunson, the state medical examiner.

Officials say the 5-foot wide, 35-feet deep hole opened up over what appeared to be an old brick-lined cistern that may date back nearly a century.

Justin de Ruyter, one of the firefighters called to the scene after police found the body Sunday, said a technical rescue team placed a tripod over the opening and used ropes to pull out Zerwas' body.

De Ruyter said he used to run across similarly built cisterns while fighting wildland fires on old farmland in eastern Washington.

"I definitely think this was an old cistern," he said. "Farmers would use them to store water underground and use a windmill or some other pump to water their dairy cows so they didn't have to take them to a creek."

Police were called Sunday to check on Zerwas after a friend in the Midwest said she had not heard from him since Thursday.

According to city records, Zerwas' home was built in 1937.

De Ruyter said that when the land was converted to residential property, cisterns were covered up with boards and dirt, and were typically forgotten.

De Ruyter said he believes Zerwas, a private investigator, was gardening when the ground collapsed.

"It looked he might have fallen backwards out of his shoes," de Ruyter said. "Once he fell in, the water is 45 to 50 degrees, and there is nothing to grab on to to climb out. It was a freak accident."

———

Information from: The Oregonian, http:www.oregonlive.com