Investigations into the Gilgo Beach murder suspect have expanded beyond New York state in the days following his arrest in connection with the Long Island slayings.

       Rex A. Heuermann, 59, a Manhattan architect, has been charged with the murders of three women whose bodies were found on Long Island's South Shore in 2010. He has pleaded not guilty.

       Rex Heuermann is shown in this booking photo released by the Suffolk County Sheriff's Department.

       Suffolk County Sheriff's Department

       Authorities in Nevada said Tuesday they are investigating a connection between the accused serial killer and Las Vegas.

       "We are aware of Rex Heuermann's connection to Las Vegas," the Las Vegas Metro Police Department said in a statement Tuesday afternoon. "We are currently reviewing our unsolved cases to see if he has any involvement."

       Police are trying to determine whether they should be searching any locations in Vegas and what those sites might be.

       This combination of undated image provided by the Suffolk County Police Department, shows Melissa Barthelemy, top left, Amber Costello, top right, Megan Waterman, bottom left, and Maureen Brainard-Barnes.

       AP

       The search for forensic and physical evidence in the Long Island case has also expanded to property Heuermann owns in Chester, South Carolina, where authorities seized his Chevrolet Avalanche in connection with the investigation. A witness to Costello's disappearance reported seeing a Chevrolet Avalanche, according to court records.

       Investigators on Tuesday were digging into Heuermann's life and checking to see if they could tie him to unsolved murders or missing persons cases throughout New York state, an NYPD official told ABC News.

       MORE: Gilgo Beach investigators comb unsolved murders for potential ties to suspect

       The suspect's DNA has been entered into a statewide database, available to all law enforcement agencies in New York.

       Heuermann was arrested in Manhattan last week and charged with the murders of Melissa Barthelemy, Megan Waterman and Amber Costello, whose bodies were found covered in burlap along Ocean Parkway on Long Island's South Shore in December 2010. He was also named the "prime suspect" in the death of Maureen Brainard-Barnes, a fourth woman discovered in the same spot, police said.

       Arrest of Rex Heuermann

       ABC NEWS

       More than 200 firearms were found at his Long Island home, officials said.

       "We wanted to take him into custody somewhere outside the house, because of access to those weapons," Suffolk County District Attorney Ray Tierney told ABC News.

       MORE: Gilgo Beach murders: What questions remain following Rex Heuermann's arrest?

       The guns explain why police would have chosen to arrest him away from home, former NYPD Chief of Detectives Robert Boyce told George Stephanopoulos on "Good Morning America" on Tuesday.

       Investigators would have searched databases and discovered that Heuermann had dozens of gun permits, Boyce said.

       "You don't want to go into that house -- you want to take him off-premise," Boyce said. "This way it's safer for everybody."

       Police officers stand guard as law enforcement searches the home of Rex Heuermann, Saturday, July 15, 2023, in Massapequa Park, N.Y.

       Jeenah Moom/AP

       MORE: Suspected Gilgo Beach killer appeared 'traumatized' after arrest: Defense attorney

       Heuermann is next scheduled to appear in court on Aug. 1.

       Heuermann's defense attorney, Michael Brown, said in a statement Monday: "There is nothing about Mr. Heuermann that would suggest that he is involved in these incidents. And while the government has decided to focus on him despite more significant and stronger leads, we are looking forward to defending him in a court of law before a fair and impartial jury of his peers."

       ABC News' Mark Osborne contributed to this story.