LOUISVILLE, Ky. -- As it turns out, Colonel Harland Sanders wasn't the only one keeping secrets.
Newly released documents from the 1970s show the FBI investigated a death threat against the iconic KFC founder and pitchman, creator of the secret recipe for the chain's fried chicken.
The warning came from someone identified as "The General." A handwritten note addressed to Sanders and his wife told the restaurant entrepreneur from Kentucky that he was in "grave danger of being murdered."
The documents show that the envelope containing the threat was postmarked Dec. 5, 1973, and had a return address in Los Angeles. The threat wasn't reported to the FBI until February 1974 by someone at KFC. The informant's name was blacked out.
Sanders died in 1980 at the age of 90 after being stricken with leukemia. His secret blend of 11 herbs and spices launched the KFC chain, and the recipe remains one of the world's most enduring corporate secrets.
KFC spokesman Rick Maynard said Thursday that Sanders received millions of letters during his life and that virtually all were positive. KFC is owned by Louisville-based Yum Brands Inc., which also owns Taco Bell and Pizza Hut.
However, the threat was likely little more than a prank, Maynard wrote in an email.
The FBI files, posted on an FBI website known as "The Vault," were first reported by the Lexington Herald-Leader on Thursday. The Sanders information had been sought previously through a Freedom of Information Act request, said FBI spokesman Jason Pack.
A federal prosecutor in Kentucky requested the investigation because of Sanders' "extensive travels and international reputation," the documents showed. The FBI's Louisville office opened the case after being notified, and leads were sent to the FBI's Los Angeles office to try to determine who sent the threat, Pack said.
The file shows that Sanders was interviewed about the threat. He indicated that the letter arrived at his post office box in Shelbyville, Ky., where he lived. He said he didn't know when it arrived because he was away on a promotional tour in Canada. He said his mail had been left unattended for about 10 days. There was no indication of why the threat wasn't reported sooner.
Sanders told authorities at the time that nothing suspicious had happened while he was in Los Angeles for a dinner for a renowned cancer research center, nor had anything happened that would make him the target of a threat, according to the documents.
Sanders was told the FBI "could not afford him protection," the files said. Local authorities were advised.
Sanders developed the chicken recipe at his restaurant in southeastern Kentucky and used it to launch the KFC chain in the early 1950s. In 1964, Sanders sold Kentucky Fried Chicken for $2 million to a group of investors.
Sanders remained the leading pitchman for the chain, and his likeness still remains central to KFC's marketing.
The chain now has more than 15,000 restaurants in 109 countries.