Authorities in Oregon are working to determine how five purebred bulls — valued at about $6,000 apiece — ended up dead, drained of their blood and with body parts almost surgically removed in late July on a ranch.

An early theory was that the mutilations were likely done by some sick cult. But lack of evidence has given way to new theories.

“A lot of people lean toward the aliens,” Deputy Dan Jenkins of the Harney County Sheriff's Office, told NPR. “One caller had told us to look for basically a depression under the carcass. ‘Cause he said that the alien ships will kinda beam the cow up and do whatever they are going to do with it. Then just drop it from a great height.”

"One caller had told us to look for basically a depression under the carcass. ‘Cause he said that the alien ships will kinda beam the cow up and do whatever they are going to do with it. " — Deputy Dan Jenkins, Harney County Sheriff's Office

5 OREGON BULLS MUTILATED ON RANCH WITH SEX ORGANS, TONGUES MISSING IN SUSPECTED 'OCCULT' RITUAL: OFFICIALS

The case recalls mutilations of livestock across the U.S. West and Midwest in the 1970s that struck fear in rural areas. Thousands of cattle and other livestock on land ranging from Minnesota to New Mexico were found dead with their reproductive organs and sometimes part of their faces removed.

Two years ago, another rancher told NPR a cow was found mysteriously mutilated about 200 miles south of Silvies Valley Ranch.

NPR reported that authorities have little evidence, but were ruling out the usual suspects: wolves, cougars and bears. There were no bullet wounds, the report said. Silvies Valley Ranch has offered a $25,000 reward for information.

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None of the scenes showed signs of a struggle and officials found no footprints, Silvies Valley Ranch Vice President Colby Marshall told the Oregonian last month.