In February, reputed Mafia captain Tony Zerilli told Detroit TV station WDIV in February 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.
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 retiring in 2012, was near the scene of the search on Monday. He said he has no direct knowledge of the search, "but it's pretty clear that's what they're doing."
"According to Zerilli and his description of the property, this seems to be it," Arena said.
Although Zerilli was in prison when Hoffa disappeared, later "he would have been in a position to have been told," Arena said.
"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."
Associated Press writer Ed White in Detroit contributed to this report.