Detectives are now checking to see if his DNA or behavior fit unsolved murders and missing persons cases in New York City, an NYPD official told ABC News.
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Additionally, the 59-year-old Heuermann's DNA has been entered into a statewide database, available to all law enforcement agencies in New York.
"Now they're not getting DNA from a discarded pizza crust, they're getting DNA directly from him, hair directly from him," law enforcement official John Miller said.
The NYPD will search missing persons cases during the time frame Heuermann was active, as well as any unsolved murders.
His DNA will also be submitted for a national search.
Police remained at the Massapequa Park home searching for clues Monday. They also searched two nearby storage units as they try to solidify the case involving the three first-degree murder charges and see if they can tie him to the other Gilgo victims.
Gilgo Beach became the focal point of the long-stalled investigation into the discovery of 11 sets of remains, including that of a toddler, all discarded along the parkway that cuts the length of a thin strip of white sand, dirt, brambles and marshes known as Jones Beach Island.
Exclusive: Surveillance video of Gilgo Beach murder suspect's arrest
The toddler and three other victims have yet to be identified. All 10 adult victims, including the toddler's mother, were sex workers, police said.
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But investigators say Heuermann might not be suspected in all of the deaths.
He has so far only been accused of killing three women -- Melissa Barthelemy, Megan Waterman and Amber Costello -- who were reported missing in 2010.
He is also the prime suspect in the death of a fourth woman who disappeared three years earlier, Maureen Brainard-Barnes.
Those four victims have become known as the "Gilgo Four."
Investigators point out that all four cases shared a number of similarities, including that all of the women had contact shortly before their disappearances with a person using a "burner" cellphone. Cellphone data in particular played a big role in the probe.
Back in January, federal investigators who were tailing Heuermann recovered a pizza box he had thrown in the garbage in Midtown Manhattan. A swab of his DNA from that pizza crust was tested and found to be a match with a hair that was discovered on one of the victims.
Investigators say the 59-year-old was still interacting with prostitutes when he was arrested last Thursday, and that there was a heightened sense of urgency, even though it's been more than a decade since the Gilgo Beach murders.
Eyewitness News reporter Darla Miles asked Louis B Shlesinger, a professor of forensic psychology at John Jay College of Criminal Justice, if he's ever come across a serial sexual killer who kills and then stops.
"Absolutely. They'll kill one, two and three and they'll stop for a significant period of time," Shlesinger said. "Four and five, and then they'll stop. Six, seven, eight and so on."
Heuermann says he is innocent, according to his lawyer.
"There is nothing about Mr. Heuermann that would suggest that he is involved in these incidents," Heuermann's defense attorney Michael J. Brown said in a statement on Monday.
Brown continued, saying his client "insisted he did not commit these crimes."
(The Associated Press and ABC News contributed to this report.)
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