The FBI has unlocked its Freedom of Information Act vault to reveal what it knows about Bigfoot. According to the newly released files, the Feds did analysis on strange hairs of unknown origin for The Bigfoot Information Center and Exhibition (BIC)—a cryptozoological society devoted to studying the mythic beast—in 1976.

What the Feds found wasn’t a shock. The hairs came from a deer, not a mythic ape.

According to the documents, BIC first wrote the FBI thanks to a likely prank played the US Army Corp of Engineers. The Engineers used to publish local atlases that detailed America’s flora and fauna. The 1975 edition for the Pacific Northwest included a reference to Sasquatch, complete with a map of possible sightings and cryptic references to the FBI. “Alleged Sasquatch hair samples inspected by FBI laboratories resulted in the conclusion that no such hair exists on any human or presently-known animal for which such data is available.”

People noticed the entry in the atlas, and it caused a flurry of news stories and more than a few letters to the FBI demanding that it release the results of the cryptid hair test.

“Will you kindly, to set the record straight once and for all, inform us if the FBI has examined hair which might be that of Bigfoot; when this took place, if it did take place; what the results of the analysis were,” Peter Byrne, director of the BIC, wrote to the FBI on August 26, 1976. “Please understand that our research here is serious. That this is a serious question that needs answering.”

The FBI politely wrote back to Byrne and explained that it had never done any analysis on cryptid hair. In response, Byrne sent the FBI a packet containing 15 hairs attached to a flap of skin. He and his team couldn’t identify the samples and wondered if the FBI could help.

“The FBI Laboratory conducts examinations primarily of physical evidence for law enforcement agencies in connection with criminal investigations,” the FBI wrote back. “Occasionally, on a case-by-case basis, in the interest of research and scientific inquiry, we make exceptions to this general policy. With this understanding, we will examine the hairs and tissue mentioned in your letter.”

On February 24, 1977, the FBI wrote back and told Byrne it had concluded its analysis. “The hairs which you recently delivered to the FBI laboratory on behalf of [BIC] have been examined by transmitted and incident light microscopy,” Jay Cochran, assistant director of the FBI wrote. “It was concluded as a result of these examinations that the hairs are of deer family origin. The hair sample you submitted is being returned as an enclosure to this letter.”