Frank Sinatra once served as a Mafia courier and narrowly escaped arrest with a briefcase containing $3.5 million in cash, entertainer Jerry Lewis told authors of a new book excerpted on Tuesday in Vanity Fair magazine.

The anecdote attributed to Lewis is one of several accounts linking the legendary singer to organized crime in the unauthorized biography "Sinatra: The Life," by Anthony Summers and Robbyn Swan and due for release May 16 by Alfred A. Knopf.

Sinatra always denied any connection to the Mafia, though FBI files released in December 1998, seven months after his death, portrayed the singer-actor as a close friend of reputed Chicago mob boss Sam Giancana.

FBI documents also suggested he had contact with mobster Lucky Luciano during a 1947 trip to Cuba and alleged that his early singing career was backed by a New Jersey-based racketeer named Willie Moretti.

The book recounts a claim the authors attribute to Lewis, one of Sinatra's "Rat Pack" compatriots from the 1960s, that Sinatra once carried money for the Mafia.

"He volunteered to be a messenger for them," Lewis is quoted as telling the authors. "And he almost got caught once ... in New York."

Lewis is quoted as saying Sinatra was going through customs with a briefcase containing "three and a half million in fifties" and that customs officials opened the case. But due to crowds jostling for a glimpse of the star, officials aborted their search.

Otherwise, Lewis said, "We would never have heard of him again."

According to Vanity Fair, the authors do not claim that Lewis witnessed the customs incident but rather related the account "as a fact of which he had knowledge."

Lewis said the incident occurred shortly after Luciano was deported from the United States to Italy in 1946.