MASSAPEQUA PARK, N.Y. (NewsNation) — Authorities are trying to determine if suspected Long Island serial killer Rex Heuermann is responsible for the deaths of four sex workers and Atlantic City, New Jersey, according to multiple reports.

ABC7 New York reports Suffolk County police are looking “around the nation,” including Atlantic City, for any possible connections to the Gilgo Beach murders in which Heuermann is a suspect.

In 2006, the bodies of four women identified as sex workers were found in Egg Harbor Township, New Jersey, which is on the Atlantic City border, according to ABC7.

Heuermann, 59, was charged last week with the murders of Amber Costello, Melissa Barthelemy and Megan Waterman. Their bodies were found in 2010.

Heuermann has pleaded not guilty.

The New York Post reports Heuermann’s DNA is being used to search for cold-case murders far beyond the New York-New Jersey area. Investigations are underway in South Carolina and Las Vegas. The Post reports Heuermann owns property in both locations.

Meanwhile, Heuermann continues to be detained at the Suffolk County jail, where he has been placed in an isolated cell for his own protection, according to police.

Heuermann is under suicide watch while two correctional officers monitor him.

He’s had no visitors and his wife has filed for divorce.

NewsNation has not been able to reach Heuermann’s family for additional comment.

Police continue to search his home in Massapequa Park, close to where the three bodies were discovered. They’ve been there for more than a week, recovering items including a life-sized doll in a glass case and a painting of what appears to be a portrait of a battered woman.

State troopers and Suffolk County police are standing guard outside the house 24/7.