Robert Foley, special agent in charge of the FBI's Detroit division, said the agency and its partners had a search warrant allowing them to dig at the property in Oakland Township, about 25 miles north of Detroit.
Officials are "here to execute a search warrant, based on information that we have involving the disappearance of Jimmy Hoffa," Foley said.
He said the warrant was sealed and details about what was sought would not be released.
Oakland County Sheriff Mike Bouchard, who joined Foley at a news conference, said it was his "fondest hope" to bring closure for Hoffa's family and the community.
Hoffa, Teamsters president from 1957-71, was an acquaintance of mobsters and an adversary of federal officials. The day in 1975 when he disappeared from a Detroit-area restaurant, he was supposed to be meeting with a New Jersey Teamsters boss and a Detroit Mafia captain.
Since then, multiple leads to his remains have turned out to be red herrings.
In September, police took soil from a suburban backyard after a tip Hoffa had been buried there. It was just one of many fruitless searches. Previous tips led police to a horse farm northwest of Detroit in 2006, a Detroit home in 2004 and a backyard pool two hours north of the city in 2003.
In February, reputed Mafia captain Tony Zerilli told Detroit TV station WDIV that he knew where Hoffa was buried and that the FBI had enough information for a search warrant to dig at the site. He said he answered every question from agents and prosecutors, and had been promoting a book, "Hoffa Found."
Foley did not mention Zerilli's claims in his brief comments Monday, but Zerilli's lawyer, David Chasnick, said his client was "thrilled" that investigators were acting on the information.
"Hoffa's body is somewhere in that field, no doubt about it," Chasnick said. He said his client wasn't making any public comments.
Chesnick said Zerilli told him there used to be a barn in the field, and that Hoffa's body was buried beneath a concrete slab inside the barn.
Zerilli was convicted of organized crime and was in prison when Hoffa disappeared. But he told New York TV station WNBC in January that he was informed about Hoffa's whereabouts after his release.
Andrew Arena, who was head of the FBI in Detroit until he retired in 2012, said Zerilli "he would have been in a position to have been told" where Hoffa was buried.
"I still don't know if this was a guess on his part. I don't know if he was actually brought here by the Detroit (mob) family," Arena said. "It's his position as the reputed underboss. That's the significance."
Keith Corbett, a former federal prosecutor in Detroit who was active in Mafia prosecutions touching on the Hoffa case, said it was appropriate for the FBI to act on Zerilli's assertions.
"You have a witness who is in a position to know, who says he has specific information," Corbett said. "The bureau has left no stone unturned."
Corbett also defended authorities for repeatedly spending time on what turned out to be dead ends.
"Anytime you look for somebody and don't find the body it is embarrassing," Corbett said. "The thing the public isn't aware of, but police know, is there are a lot of dead ends in an investigation"
Associated Press writer Ed White in Detroit contributed to this report.