Authorities Monday unearthed a suspected Mafia graveyard in an overgrown New York City vacant lot where at least five men — including the unlucky guy who accidentally ran over and killed Gambino crime family don John Gotti's son in 1980 — are believed to have been buried.

FBI agents, backed by cadaver-sniffing dogs, a helicopter and heavy construction equipment, swooped down on the site on 75th Street in Ozone Park, Queens, (search) specifically searching for at least two bodies believed to have been stuffed into steel drums, and three more wrapped in canvas, sources said.

In addition to Gotti's tragic former neighbor, those believed to be buried there include Tommy DeSimone — the crazy hit man portrayed by Joe Pesci (search) in the movie "GoodFellas" — and Bonanno crime family capos Dominick "Big Trin" Trinchera and Philip "Philly Lucky" Giaccone, sources said.

The fifth man was described as a thug who refused to carry out the hit on DeSimone, only to wind up being personally killed by a furious Gotti.

Sources added that the five men may be just the beginning of a long list of victims hidden in the Mafia dumping ground.

As many as 15 more corpses could be buried at the empty, weed-choked spot — most of them the remains of victims killed by the Gotti-run Gambino family (search), sources said.

"From what I understand, there are a lot of things down there," one source said of the site between Blake and Dumont avenues on the Brooklyn border.

At the top of the list of suspected victims entombed beneath the three to four feet of concrete is John Favara, Gotti's one-time neighbor in Howard Beach.

The 51-year-old dad of two was driving home from work March 18, 1980, when Gotti's 12-year-old son, Frankie, who was on a minibike, darted in front of his car and was struck and killed.

After four months of being terrorized by Gotti goons, Favara disappeared after leaving work.

Witnesses said they last saw him being ambushed and then beaten bloody by Gotti thugs before being thrown into the back of a van.

Meanwhile, Trinchera, an obese 350 pounds, and Giaccone were fatally gunned down along with fellow capo Alphonse "Sonny Red" Indelicato during a nearly botched rubout at a Brooklyn social club on May 5, 1981.

Indelicato's body was found wrapped in canvas later that month at the same site now being excavated. He had been shot once in the head and twice in the chest.

The bodies of Trinchera and Giaccone — part of a trio accused by Bonnano family (search) honcho Joe Massino of trying to undermine his control — were never found.

The hot-headed DeSimone, a mob associate, was rubbed out in 1978 after flying into a rage and killing two close pals of Gotti.

Law-enforcement sources said they launched the massive dig based on new information from several informants.

The feds said the stunning development at the graveyard came as they also were finally piecing together exactly what they believe happened to Favara in his final minutes.

They say it appears Favara, a manager at a Castro Convertible plant in New Hyde Park, L.I., was eating at a diner near his office the day he disappeared when a group of Gotti's goons pulled up outside.

The group — including Gotti's brother Gene, John Carneglia, Wilfred "Willie Boy" Johnson and Anthony "Tony Roach" Rampino — ambushed Favara as he left, beating him to a pulp with a baseball bat, the sources said.

Favara was then shoved into a van and shot, they said.

The sources said he was then driven to an auto-body chop shop owned by Carneglia, and his body dismembered.

The group put the body parts and cement mix in a drum before burying the steel container at the lot, the sources said.

John Gotti, who has since died of throat cancer, was reportedly in Florida on vacation at the time.

Sources said the burial of Favara's body by the Gambinos and of the three capos by the Bonannos at the same spot was extremely unusual.

Organized-crime families rarely use the same spot to dump their victims, since those involved in the hits aren't supposed to discuss the killings with anyone not directly involved in them.

But federal sources noted that Gotti and Massino were old buddies, having grown up in the same Howard Beach neighborhood. They say this might account for the move.

Law-enforcement workers at the lot yesterday said it had been deemed a flood zone, and that construction crews over the years built it up with concrete so that it wouldn't be saturated with water and ruin their equipment.

Now, with up to four feet of concrete to rip up and sift through, the agents said the dig could last several weeks.

"Two weeks of digging — that's what they have planned," a source at the site said.

A spokesman for U.S. Attorney Roslynn Mauskopf declined to comment.

Victoria Gotti, John's widow, yesterday griped that he's now an easy target for those wanting to pin Favara's disappearance on him.

"They blame too much on John Gotti," she said.

Of Favara — whom she herself once attacked with a baseball bat shortly after her son's death — she said only, "I didn't really know him."

But neighbors said Favara's story was tragic from the start, beginning with the accident.

Just after that, his family started receiving threatening mail. Then his car was stolen from in front of his house and later recovered — with "Murderer" spray-painted on it.

Favara was so distraught that he frantically gave his wife power of attorney in the days after the accident and tried to sell their house so they could escape the area.

He was two days away from closing on the sale of their house, which was just around the corner from the Gottis, when he disappeared.

Margherita Lange, 39, who now lives at the Favara home, said, "I never really think about it because it happened so long ago.

"But I wish someone had told me it was his house when I had bought it. If I had known, I wouldn't have bought the house."