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 age 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, FBI spokesman Jason Pack said.

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.

Brooke Shields heads back to Princeton

PRINCETON, N.J.  — Brooke Shields is going back to school.

The 1987 graduate of Princeton University is giving the university’s important and often whimsical Class Day address as part of graduation weekend.

Shields was already a star of films like “Blue Lagoon” and “Endless Love” when she arrived at Princeton. She graduated as a French major with honors.

Speakers at other Class Day ceremonies in recent years have included comedian Stephen Colbert, former President Bill Clinton and news anchor Katie Couric. The speaker at the May 30 event was invited by the New Jersey school’s graduating class.

New York City Mayor Michael Bloomberg will speak at the May 29 baccalaureate.

Lil Wayne’s cops weren’t

BLOOMINGTON, Ind. — Two security guards face charges of impersonating police officers after they escorted rapper Lil Wayne to an Indiana nightclub.

WISH-TV reported that 43-year-old Ronald Andre Harrod and 23-year-old Larry Lee Richardson of Indianapolis wore police-type uniforms and gun belts as they escorted Lil Wayne to a Bloomington nightclub Wednesday.

Police said Richardson led a caravan of tour buses in a car that had flashing red and blue lights and sirens blaring. Harrod was behind the caravan in another car that also had red and blue flashing lights.

Sheen told not to smoke onstage

TORONTO — Canadian health officials warned Charlie Sheen not to smoke onstage Thursday during the Toronto stop of his “My Violent Torpedo of Truth” tour.

Sheen, who has frequently puffed on a cigarette onstage during earlier tour stops, was to perform his one-man show at Massey Hall for two nights.

Ontario Health Promotion Minister Margarett Best said health inspectors would be watching to ensure Sheen didn’t light up onstage. She also offered Sheen help on kicking the habit, saying he should call the province’s quit line.

It is illegal to smoke indoors in Ontario and celebrity cigarette habits have caused controversy in the past. Sean Penn lit up during a Toronto International Film Festival a few years ago, resulting in fines against a local hotel.