Agents have planned a Monday dig in a Detroit-area field Monday based partly on information from Tony Zerilli. In an interview earlier this year, Zerilli said Hoffa was buried in a field 20 miles north of Detroit, where he was last seen in 1975.
The FBI researched his claim for months before seeking authorization from the court to excavate the field.
Hoffa was last seen July 30, 1975, outside a restaurant near Detroit. He was 62 at the time, and FBI officials said the disappearance was likely linked to Hoffa's push to regain power in the Teamsters, and use the mob's influence over union pension funding. Hoffa was president of the Teamsters union until 1971.
A previous tip led to a suburban Detroit home, where the FBI took soil samples. The samples showed no evidence of human remains, however.
Zerilli said that a Mafia enforcer informed him of the real burial location, in Oakland Township. The site, he said, was originally intended to be Hoffa's temporary grave. The informer told Zerilli that Hoffa was abducted and taken to the Buhl Road site and put in a shallow grave. The remains were set to be moved to another spot after the search for Hoffa died down.
Zerilli, now 85, was convicted of crimes in connection with several instances of organized crime in Detroit. He was second-in-command of the Detroit mafia and son of Detroit mafia founder Joe Zerilli. He was freed in 2008 after his last prison sentence, but was still in jail when Hoffa disappeared.
The search is seen as a "giant black eye for the FBI," said mob expert Scott Bernstein. "That said, you have to follow this lead because it's probably the most credible lead the FBI's ever gotten on this case."