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 "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"