What happened to Jimmy Hoffa? After 48 years, will the riddle ever be solved?

CHICAGO (WLS) -- It's been nearly a half century since Jimmy Hoffa vanished without a trace and what happened to the former Teamster boss remains one of the oldest crime mysteries in America.

It may be fitting that the "R" in James R. Hoffa is for Riddle; his actual middle name, and the maiden name of Hoffa's mother.

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On July 30, 1975 the embattled labor union boss was scheduled to meet a pair of top mob figures at a suburban Detroit restaurant. Instead Hoffa met his death, according to federal law enforcement officials, and so began a riddle that wound through Chicago and continues to this day.

What happened when Hoffa pulled into a restaurant parking lot near Detroit 48 years ago Sunday?

"I do believe there's probably some associates and people who are involved that may still be alive. They'd be pretty old by now. And I think information is probably passed down generationally and the mafia. There are people who do know how this happened and where it is," said Ed Farrell, ABC7 law enforcement expert.

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But not many people see the Hoffa case as still solvable, according to Farrell.

As the I-Team first reported 10 years ago, federal law enforcement officials believe the Chicago Outfit had a hand in Hoffa's disappearance. That is based mostly on interviews with mob insiders and an apparent connection to the late Chicago mob boss Frank Calabrese Sr., a hoodlum known in organized crime circles as Frank "The Breeze."

Calabrese's FBI file, obtained by the I-Team, details a meeting in Missouri the week that Hoffa vanished; part of the so-called "Hoffex" investigation, the FBI's code name for the case.

In the bureau's file cabinets are links between Hoffa, Chicago Outfit bosses and the Teamster's Central States Pension Fund which is long thought to be key components of the crime riddle.

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Is 48 years too long to resolve the case or is it going to be open ended forever?

"It's not too long. I think probably the best case scenario for the American public would be a case closure," Farrell said. "Obviously most of the offenders who probably were involved in this are probably dead. There would be senior mafia officials, they'd be in their 80s, 90s or 100s so I think getting a prosecution would be near impossible, but I do think they could probably close the case. They probably could get some information as to where the body is, get the physical evidence and close the case and potentially solve who did it."

As the riddle remains, thousands of hours and millions of dollars have been spent on running down Jimmy Hoffa tips and clues, checking car crushers and meat grinders, digging up back yards, construction sites and landfills.

To this day, the consensus among informed federal agents and mob-ologists is that Hoffa was killed in Detroit and his corpse quickly dissolved in an acid vat, never to be found.