OAKLAND TWP. (WWJ) – Federal agents searching for the body of former Teamsters chief Jimmy Hoffa believe they are about to crack one of America’s biggest unsolved mysteries.

CBS News has confirmed a suspicious concrete slab was retrieved by investigators from the Oakland Township field where they have been digging for any sign of Hoffa. It’s too soon, however, to know whether the slab is anything more than part of an old foundation for a barn.

[UPDATE: Later, Tuesday, officials said a cadaver dog reacted to some scents at the site. Read more here].

The dig — the latest in what’s been nearly a 40-year search — is reportedly the result of extensive FBI interviews with former mobster Tony Zerilli.

Zerilli, now 85, was convicted of organized crime as a reputed mafia captain. He was in prison on July, 30 1975 — when Hoffa disappeared from a Bloomfield Township restaurant — but says he was informed about Hoffa’s whereabouts after his release.

Zerilli, who was second in command with the Detroit mafia, said he was told by a mafia enforcer that Hoffa was abducted, killed, and brought to the Buhl Road site. The original plan, according to the mobster, was to bury Hoffa there temporarily, then later move his body near a hunting lodge in northern Michigan.

Instead of focusing their attention Up North, investigators on Monday zeroed in on the property in northern Oakland County — which was once owned by Betty Speezie’s aunt.

“It’s all gone now, but there was a house, a milk house, a barn and a garage,” Speezie told WWJ’s Kathryn Larson.

“It was pretty dilapidated looking, it wasn’t well cared for,” said Ruth Lowe, Speezie’s neighbor.

Both women say they’re stunned by Hoffa once again making all the headlines. Lowe said she never thought the search would take place in her neighborhood.

“I never gave it a thought, no. It’s hard to believe it, that he might be there,” she said.

But Speezie said she believes the hype, and for good reason — her aunt sold the property to the Tocco’s, another mobster family.

“After my aunt sold it then, she didn’t know anything about the mob, I mean, they were just people who had the money, it was for sale, and she sold it to them,” she said.

And there’s one place in particular Speezie thinks investigators should focus on.

“The barn. They could have gone right around to the back, backed right up there and it was dirt, inside the barn, it was dirt on this side,” she said. “Nobody would have known a thing, it would be very secretive.”

The search, which is expected to last about a week, will resume Tuesday morning.

MORE: Dig For Hoffa Turns Up Gawkers, Few Clues

Feds Digging In Oakland Township Searching For Hoffa’s Remains