Correspondent Dean Reynolds blogs from a horse farm outside Detroit: They are searching with a backhoe and shovels. Scores of FBI agents… Digging away at four separate sites on an 85 acre horse farm outside Detroit. Agents began the dig on Wednesday based on a tip they deemed credible. Agent Daniel Roberts said it was the best he’d seen in two years of working out of the Detroit FBI office. They’ve called in archaeologists, anthropologists, engineers and architects… As well as a group of Michigan State grad students… Cadaver dogs and representatives of the FBI lab in Washington. Unfortunately for the FBI and everybody else interested in this… There have been many, many tips and none has panned out. Jimmy Hoffa ran with a pretty rough crowd… Including mobsters… Two of whom he was to lunch with on that afternoon back in July 1975. They evidently stood him up. But sometime after 2 p.m. that day, witnesses say he got into a car with a number of burly males inside and was driven away – never to be heard from again. Shot or garroted by hit men from the mafia or Teamsters Union rivals… There is little doubt that Hoffa is dead. But the fact that his body never turned up turned his disappearance into the stuff of legend… At least for people over 40. At various times, there’s been speculation that he’s buried near Detroit… Or that he lies at the bottom of one of the Great Lakes… Or that he rests in the end zone at Giants Stadium in the New Jersey Meadowlands… Or somewhere along the Jersey Turnpike… or in a coal mine in Pennsylvania. Nor was it likely that he rests peacefully in a coffin somewhere. Instead, legend has it that he was melted in a smelter… Wedged into a car-crusher… Dropped into a vat of boiling animal fat or mixed with concrete. Yikes! My favorite is that Hoffa is still alive and living in Brazil… Where he supposedly went in the company of local Detroit go-go dancer. Whatever… The dig looks pretty extensive from the shots I can see taken by a helicopter crew. The news media on the ground are being kept far away from the area made muddy by two weeks of rain. Agent Roberts said they could be digging for the next couple of weeks at least.