Investigations into suspected Long Island serial killer Rex Heuermann now span several states — with cops in Las Vegas among those reviewing unsolved cases for possible ties.

While the 59-year-old architect lived in Massapequa Park and worked in Manhattan, where he was busted, he also had a property portfolio including a planned retirement home in South Carolina and timeshares in Sin City.

The Las Vegas Police Department confirmed it was “aware” of the Gilgo Beach serial killing suspect’s connections to the city and already investigating possible links to crimes.

“We are currently reviewing our unsolved cases to see if he has any involvement,” a spokesperson told The Post.

The married dad of two has owned property in Sin City since at least 2004, according to records obtained by the Las Vegas Review-Journal.

That year he bought a timeshare just off the Strip for $51,298, selling it for the exact same amount in 2013, three years after the bodies of the “Gilgo Four” were found a few miles from his Long Island home.

He still owns another two-bedroom timeshare at Club De Soleil, which promises “the taste of a lavish European lifestyle” just “a few minutes from” the Strip, the paper noted.

He bought that property with his wife, Asa Ellerup, for nearly $17,000 in 2005, the paper said.

It boasts numerous shared facilities, including “a resort-style pool and spa, tennis court, putting green” and gym.

Cops in South Carolina earlier confirmed they were helping the Gilgo Beach task force with searches at an isolated area in woodland where Heuermann reportedly planned to retire. 

A Chevy Avalanche — like the one key to first linking Heuermann to the murders — was seen being hauled away from the area, where the suspected killer’s brother, Craig, already lives.

The Post previously revealed that the NYPD is comparing Heuermann’s DNA to its backlog of cold cases. 

But the search is already being extended far wider, former NYPD Chief of Detectives Robert Boyce told ABC’s “Good Morning America.”

“I made some phone calls yesterday to see what they were doing. They’re looking at all missing persons who have never been found and see if they can put those together,” Boyce said.

“Not just in Suffolk [County], but throughout the tri-state area,” he said of the suspected serial killer who’s been “free” in the 13 years since he allegedly murdered sex workers.

“There’s also the FBI that’s looking at national issues as well.”

Heuermann has pleaded not guilty to murdering Melissa Barthelemy, Megan Waterman and Amber Costello.

He has also been named the prime suspect in the murder of Maureen Brainard-Barnes.

Suffolk County police officials have also confirmed they have not ruled out ties to six other bodies found in a similar area in 2010 and 2011.