The new dig began after an alleged mobster, Detroit-area La Cosa Nostra underboss Anthony Zerilli, tipped the FBI to the location.
"Hoffa's body is in the field, no doubt about it," David Chasnick, attorney for Zerilli, told media Monday afternoon. "I'm told the FBI believes he's there, 100 percent. They wouldn't do all this work and get the warrant and invade this property if they weren't certain."
Hoffa was abducted, hit in the head with a shovel and buried alive in a shallow grave on a former farm once owned by mob boss Jack Tocco, Zirelli claimed. The farm is about a half-hour's drive north of the Machus Red Fox, the restaurant in Bloomfield Township where Hoffa was last seen alive.
The FBI would not say what -- if anything -- was discovered on the first day of the search Monday, but said they expected to resume their efforts around 8 a.m. Tuesday morning. On Monday, they focused on a spot about 150 yards from the intersection of Buell and Adams roads, where a line of trees and police barricades blocked the view of gathered onlookers.
Hoffa was the Teamsters Union president until 1971, and it is believed he was killed because he was making a play to retake the job after spending four years in prison for fraud and jury tampering. He disappeared the afternoon of July 30, 1975, after reportedly meeting with two mafia bosses. He was declared legally dead in 1982.
Zerilli was in prison when Hoffa disappeared in 1975, but said he was informed of the location of the body when he was released. His high position within "the outfit" lends credence to the claim, said Jim Hoffa, Jimmy Hoffa's son.
But Zerilli's tip is hardly the first to send federal investigators scrambling to dig up some abandoned field or paved-over parking lot.
In fact, 14 other tips have lead to searches, including six in the past decade:
Celebrity Couples of 2014 [PHOTOS]