(CNN) -- Police will drill outside a suburban Detroit residence Friday in the search for Jimmy Hoffa, the labor strongman whose disappearance is one of the most notorious and mysterious in U.S. history.
A tipster told police that a body was buried at the spot in Roseville, Michigan, at around the same time the Teamsters boss disappeared in 1975.
The tipster did not claim it was Hoffa's body, authorities said.
Police Chief James Berlin told CNN Thursday that while the tipster's information seems credible, he's not convinced the body is Hoffa's because of the timeline. He spoke with the tipster on August 22, and believes the person did see a burial.
The tipster did not come forward sooner out of fear, said Berlin.
Dan Moldea, author of "The Hoffa Wars," told CNN the tipster, a former gambler, contacted him on March 30. The tipster used to do business with a man who had ties to Anthony Giacalone, an organized crime figure who was supposed to meet Hoffa the day he disappeared, Moldea said.
"I am very skeptical," Moldea said of the planned dig. If Hoffa's burial had taken place at the spot, it would have been in full view of the neighborhood, the author argued.
And if Hoffa's body was disposed of, it would have been done in a way that no evidence would be left years later, he said.
At 10 a.m. Friday, crews will begin digging, police chief Berlin said. It shouldn't take long to get a sample, which will be taken to a forensic anthropologist at the University of Michigan for analysis.
The reading will determine whether there are human remains at the site, but will not identify them, Berlin said.
"It took us a while to get the proper equipment to do what we're going to do. If this is a person, they've been down there for 35 years. What's a few more days?" Berlin said.
Results from the soil testing should be available next week, the chief told CNN Wednesday.
"If they are positive, we will then start excavating," Berlin said.
The alleged burial site is under a concrete slab, and the residence is occupied by new homeowners, who've been "cooperative and excellent to police," Berlin said.
The FBI in Detroit had no comment on the planned search.
Hoffa remains among America's most famous, and in many ways infamous, missing people. His presumed death has vexed investigators for four decades.
One of the most powerful union leaders at a time that unions wielded a great deal of sway over elections -- and were notoriously tied to organized crime -- Hoffa was forced out of the organized labor movement when he was sent to prison in 1967.
He served time for jury tampering and fraud at a federal penitentiary in Lewisburg, Pennsylvania, until being pardoned by President Richard Nixon on December 23, 1971 -- on the condition that he not try to get back into the union movement before 1980.
Two weeks before Hoffa's disappearance in 1975, federal investigators discovered that hundreds of millions of dollars had been stolen from the Teamsters' largest pension fund, Time magazine points out in its list of the top 10 most famous disappearances.
Hoffa, then 62, was last seen July 30, 1975, at Machus Red Fox restaurant in suburban Detroit. He was there ostensibly to meet with reputed Detroit Mafia street enforcer Giacalone and Anthony Provenzano, chief of a Teamsters local in New Jersey, who was later convicted in a murder case. Both men have since died.
Hoffa believed Giacalone had set up the meeting to help settle a feud between Hoffa and Provenzano, but Hoffa was the only one who showed up for the meeting, according to the FBI.
Giacalone and Provenzano later told the FBI that no meeting had been scheduled.
The FBI said at the time that the disappearance could have been linked to Hoffa's efforts to regain power in the Teamsters and to the mob's influence over the union's pension funds.
Police and the FBI have searched for Hoffa intermittently ever since.
In September 2001, the FBI found DNA that linked Hoffa to a car that agents suspected was used in his disappearance.
In 2004, authorities removed floorboards from a Detroit home to look for traces of blood, as former Teamsters official Frank Sheeran claimed in a biography that he had shot Hoffa. Sheeran died in 2003.
Investigators ruled blood found in the house was not Hoffa's. The FBI has a sample of his DNA from a hair brush.
Two years later, the FBI razed a horse barn in Michigan following what it called "a fairly credible lead."
But the disappearance remains unsolved.
Urban lore long suggested that Hoffa was buried around the end zone at the former Giants Stadium in New Jersey.
As TruTV puts it, the mystery surrounding Hoffa is not simply a "whodunnit."
"The likely suspects are all known, and their motives are well documented. The question is: Where? What exactly did they do to Jimmy Hoffa, and where did they dispose of his body?"
But over the years, numerous theories have been floated. In 1987, Joe Franco -- a former Hoffa strong-arm -- and a New York Times reporter published "Hoffa's Man," which Fortune described as "the hair-raising inside story of Jimmy Hoffa."
"Rather than being kidnapped by rival union forces as law enforcement authorities have long speculated, Franco says Hoffa was abducted by two federal agents," Fortune reported. "He thinks they drove Hoffa to a nearby airport, took off in a small plane, and pushed him out over one of the Great Lakes. Franco says he did not tell federal investigators this bizarre, and unverifiable, story because they would not grant him immunity."
Hoffa's son, James P. Hoffa, is the current president of the Teamsters.