Just conceivably, beneath the drive of a modest bungalow-style house in the north-eastern suburbs of Detroit, there lies the answer to one of America's most enduring mysteries: what happened to Jimmy Hoffa? One of America's most powerful post-war union leaders, for 13 years the president of the International Brotherhood of Teamsters, Hoffa disappeared without trace on a summer afternoon more than 37 years ago, at a restaurant 22 miles east of where his remains might now be buried.
The general assumption is that he was victim of a Mafia killing. For decades the Teamsters, who drew their membership above all from the freight, shipping and transport sectors, were riddled with corruption and links to organised crime. Hoffa himself spent four years in prison after being convicted for bribery and fraud, before being pardoned in 1971 by President Richard Nixon, on the condition that he stay out of union activities until 1980.
But Hoffa was determined to regain control of the Teamsters, and far sooner than that. No-one has ever been charged in connection with his disappearance, but in a detailed 1976 report on the case, the FBI concluded he was killed on the orders of mob bosses who feared his return to power would threaten their control of the union's lucrative pension fund.
Over the years countless theories have been advanced about Hoffa's fate. Several burial sites have been reported – the most recent of them in 2006, when the FBI spent $250,000 – razing a barn in the process – on a convict's tip that his remains were to be found at a horse farm once owned by a corrupt Detroit Teamsters official.
Other tales have Hoffa's final resting place as the concrete foundations of the old Giants football stadium, a few miles west of Manhattan, or a support pillar of a New Jersey freeway. Others have claimed his body was rendered for fat in a mob-controlled food processing plant; even that he was fed to alligators in a Florida swamp.
But every lead has been fruitless, and the odds are this latest one will prove a wild goose chase too. It began with a tip to Dan Moldea, a Washington-based investigative journalist, and author of the 1978 book "The Hoffa Wars", from a man who claims to have seen someone being buried in a secluded part of the driveway at the house in Roseville around the time that Hoffa disappeared, on 30 July, 1975.
Mr Moldea in turn referred the informant to the FBI, who deemed the new witness credible. "This is not a mob guy," Mr Moldea told The Detroit News about the tipster, who has terminal cancer. "He's not connected. He's just a guy in the right place at the right time, or the wrong place at the wrong time. He's scared to death right now."
Initial tests at the site have indicated an "anomaly", and further soil tests are being carried out today. "If they are positive, we will then start excavating," Roseville police chief James Berlin said. "It could be anybody down there, could be nobody."
The house at Roseville is about a half hour's drive from where Hoffa was last seen, at what was then the Machus Red Fox restaurant. He went that day to the Red Fox, where he had earlier told friends, he had a 2pm meeting with Anthony ('Tony Jack') Giacalone, a member of the Detroit mafia, and Anthony ('Tony Pro') Provenzano, a New Jersey Teamsters official with strong mob connections.
But neither showed up, and around 20 minutes later Hoffa telephoned his wife from inside the restaurant to say he'd been stood up. He then went to the car park and was never seen again. The next day, Hoffa's green Pontiac car was found at the restaurant. And there the trail ended.
Both Giacalone and Provenzano established alibis. Three weeks later, police dogs found Hoffa's scent in a car that Charles (Chuckie) O'Brien, a close associate of the Teamster boss, had borrowed from Giacalone's son Joey on the day of the disappearance. But O'Brien denied any involvement, and investigators could never prove otherwise. On 30 July 1982, seven years after he vanished, Hoffa was declared legally dead.
Where real life has provided no answer, art has stepped in. Hoffa has featured in two TV series, one of them about the life of Robert F. Kennedy, who as a Senate lawyer and then as his brother's attorney-general in the early 1960s, pursued Hoffa relentlessly as part of his crackdown on crime and racketeering. Most famously, Hoffa was portrayed by Jack Nicholson in the 1992 film of that name, in which Hoffa is shot by a Mafia hit man.
Meanwhile the mystery persists, and Hoffa's daughter Barbara Crancer, a retired administrative judge, is sceptical. "I don't put much credence into it," she told the Detroit Free Press. "I don't think the case will ever be solved. Too many people are dead and gone. But as his daughter, I would like to have a body to bury."
Missing: Famed disappearances
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The diplomat helped save tens of thousands of Jews from the Nazis by issuing them with Swedish passports while serving in Budapest. He went missing when taken prisoner by the Soviets in 1945, and his family are still campaigning to discover his fate.
Following the Bolsheviks' 1917 execution of her father, Tsar Nicholas II, rumours persisted for 90 years that Anastasia had somehow escaped. It was only in 2007 that a grave was discovered which later yielded DNA samples linked to the final missing Romanov children.