He said about 40 agents were involved in an operation that covered about an acre. The FBI has not put a cost on the search, but Foley said it's more important to solve a case.
"With any investigation we consider cost-benefits analysis," he said. "The FBI and its partners are no corporations. We do not have a profit margin as a bottom line."
Detroit FBI spokesman Simon Shaykhet said Wednesday that there was no connection between the dig for Hoffa's remains and an excavation on Tuesday at the house in New York once occupied by gangster James Burke. Burke, a Lucchese crime family associate known as "Jimmy the Gent," was the inspiration for Robert De Niro's character in the 1990 Martin Scorsese movie "Goodfellas."
Hoffa's rise in the Teamsters, his 1964 conviction for jury tampering and his presumed murder are Detroit's link to a time when organized crime, public corruption and mob hits held the nation's attention. Over the years, authorities have received various tips, leading the FBI to possible burial sites near and far.
In 2003, a backyard swimming pool was dug up 90 miles northwest of Detroit. Seven years ago, a tip from an ailing federal inmate led to a two-week search and excavation at a horse farm in the same region. Last year, soil samples were taken from under the concrete floor of a backyard shed north of the city. And detectives even pulled up floorboards at a Detroit house in 2004.
No evidence of Hoffa was found.
Other theories have suggested he was entombed in concrete at Giants Stadium in New Jersey, ground up and thrown in a Florida swamp or obliterated in a mob-owned fat-rendering plant.
Zerilli, now 85, was in prison for organized crime when Hoffa disappeared. But he told New York TV station WNBC in January that he was informed about Hoffa's whereabouts after his release. His attorney, David Chasnick, said Zerilli is "intimately involved" with people who know where the body is buried.
Details are in a manuscript Zerilli is selling online.