Federal agents are digging up a field in suburban Detroit in search of the remains of ex-Teamsters leader Jimmy Hoffa, last seen alive when he left for lunch with two mobsters 38 years ago.

They started digging Monday at a site in Oakland Township, about 25 miles north of Detroit. Agents called it a day about 7 p.m. and plan to resume the search Tuesday morning.

The effort comes after reputed Mafia captain Tony Zerilli said Hoffa was buried beneath a concrete slab in what used to be a barn on the site.

Hoffa was Teamsters president from 1957 to 1971.

He disappeared in 1975 after going to a Detroit-area restaurant for what was supposed to be a meeting with a New Jersey Teamsters boss and a Detroit Mafia captain.