The FBI has summoned archaeologists and anthropologists in one of the most intensive searches in years for the body of former union leader Jimmy Hoffa.
Authorities brought in heavy equipment to scour a horse farm in Michigan for the body of the former Teamsters boss who vanished in 1975.
A team of investigators work to recover crime evidence connected to the 1975 disappearance of Jimmy Hoffa
Daniel Roberts, agent in charge of the Detroit FBI field office, would not disclose what led agents to the farm, but said: "This is probably a fairly credible lead. You can gather that from the number of people out here."
No trace of Mr Hoffa has ever been found, and no one has ever been charged in the case. But investigators have long suspected that he was killed by the mob to keep him from reclaiming the Teamsters presidency after he got out of prison for corruption.
The farm, just outside Detroit, used to be owned by a Teamsters official. And mob figures used to meet at a barn there before Mr Hoffa's disappearance, authorities said.
Investigators began combing the area on Wednesday, and the search continued yesterday and included the use of heavy construction equipment. Mr Roberts said it would probably involve the removal of a barn.
Authorities also led cadaver dogs across the property, and the FBI called in anthropologists and archaeologists from Michigan State University.
Mr Roberts said he expects the search to go on for at least a couple of weeks.
Mr Hoffa was last seen on a night he was scheduled to have dinner at a restaurant about 20 miles from the farm. He was supposed to meet with a New Jersey Teamsters boss and a Detroit Mafia captain, both now dead.
Over the years, Mr Hoffa's disappearance spawned endless theories — that he was entombed in concrete at Giants Stadium in the New Jersey Meadowlands; that he was ground up and thrown to the fishes in a Florida swamp; that he was obliterated in a mob-owned fat-rendering plant that has since burned down.
In 2003, authorities searched beneath a backyard pool a few hours north of Detroit but turned up nothing. The following year, they pulled up the floorboards on a Detroit home and found bloodstains, but the blood was not Mr Hoffa's.
A law enforcement official in Washington said the latest search was based on information developed several years ago and verified more recently.
AP