A search in a field near Detroit for ex-Teamsters boss Jimmy Hoffa ended Wednesday, and as with so many past attempts to find him, authorities walked away empty-handed, the FBI said.

Authorities resumed digging in the field Wednesday morning, and a law enforcement source said the search was expanded to a site where a house once stood.

John Anthony, a former FBI special agent involved in the original 1975 hunt for Hoffa, said the tip from alleged mobster Tony Zerilli which prompted this week's renewed search was the most credible he's heard since Hoffa's disappearance - though he still has his reservations, he said.