David Morgan Millionaire's wife missing since 1980, and his girlfriend vanished in 2000

Millionaire Las Vegas landowner David Morgan is being investigated in connection with a fourth missing person's case.

"We will be looking into one more case," Las Vegas police Lt. Brad Simpson, head of the missing persons detail, said Thursday. He would not say which missing person's case that is.

Simpson said his unit has received several reports linking Morgan to other missing people. The one that has been added to the investigation is the most valid so far, he said, but others may be added later.

"We have others we are going to look into. They may not all be true. We have to confirm the validity of these reports," Simpson said.

On Tuesday, Morgan, 71, was arrested in Kingman, Ariz., on a charge of murder with a deadly weapon in the death of his wife's lover, Gabriel Vincent, more than 27 years ago.

Morgan was booked into the Clark County Detention Center late Wednesday.

From Sunday through Thursday evening, Las Vegas police dug up a site in the southwest valley where they suspected Morgan had buried Vincent. The property, in the 3200 block of West Sunset Road, near Polaris Avenue, is owned by Morgan. Clark County has assessed its taxable value at nearly $4 million.

After digging through asphalt, concrete and dirt behind LT Eventions, an event design, decoration and production company, police came away empty-handed, Simpson said. The digging is not expected to continue today.

"We have exhausted the areas covered in the search warrant," Simpson said, lamenting that nothing was found.

"I wish it was an excellent, perfect lead," he added.

Police said the many long-standing questions surrounding Morgan and the disappearances of people connected to him required that police run the lead down, and to do that, they needed to dig up the site.

Morgan's wife, Marie Morgan, vanished in 1980. His long-time girlfriend, Diana Leone, disappeared in 2000.

Police have long suspected that David Morgan was involved in those disappearances but have never charged him.

Detectives opened the Vincent case after Morgan's former employee Fred Hacket told police he saw Morgan shoot Vincent and helped bury his body near Indian Springs in November 1979.

One reason police are convinced that Vincent, Marie Morgan and Leone are dead and didn't run off to live somewhere else is that they never contacted friends or relatives.

Records such as driver's licenses expired after they disappeared.

Vincent didn't renew his license when it expired in 1980. A check of every state's department of motor vehicles failed to find a license for him anywhere.

A search of information databases across the nation also came up empty.

Vincent also never picked up his last check from Sunrise Hospital and Medical Center, where he had been working as an orderly.

According to witness statements in the arrest warrant for Morgan, Vincent rented a storage facility from Morgan at 3200 W. Teco Ave., near where police did their digging.

Vincent and Marie Morgan were having an affair in 1979, and he took pictures of the sexual acts and tried to blackmail David Morgan with them, Marie Morgan's sister told police.

David Morgan had bragged about staking out Vincent and gunning him down, shooting him in the groin and the chest, outside the storage facility off Sunset Road, according to the arrest warrant.

But that story could not be corroborated until detectives found Hacket thanks to advancements in computer technology, the warrant said.

Hacket told police that he had given a .38-caliber revolver to Morgan. He also said that, at the storage units on Teco in 1979, he saw Morgan pull out a gun, point it at a man he believed was Vincent, and shoot him in the chest, the warrant said.

Hacket told police that he and Morgan drove Vincent's body north on U.S. 95 toward Indian Springs and buried it in the desert near the turnoff for Mount Charleston, according to the warrant.

Investigators recently came to suspect that Vincent's body had ended up on Morgan's property off Sunset, but they have not said what led them to that conclusion.

Vincent, who was 55 or 56 when he disappeared in 1979, was arrested 14 times between 1942 and 1975. He was arrested by authorities in the Las Vegas Valley on Feb. 23, 1979, because he didn't register his address, which is required for felons.

Vincent previously was convicted of robbery, auto theft, illegal possession of a weapon, and burglary.

He served time in prison, was released in 1971 and was on probation until 1976, according to the police affidavit.

Morgan was charged numerous times in Clark County, mostly domestic violence charges, but he was never convicted, according to Las Vegas Justice Court records.

In several incidents, the key witness, Leone, refused to testify.