Police are searching for body parts and other potential “trophies” at a Long Island storage locker linked to accused Gilgo Beach serial killer Rex Heuermann, authorities said Monday.

Investigators executed a search warrant at Omega Self Storage in Amityville over the weekend after scouring Heuermann’s “cluttered” home in Massapequa Park — and are now honing in on finding possible grisly remnants of the killings, Suffolk County Police Commissioner Rodney Harrison told WPIX11 News.

“He’s a monster,” Harrison said.

He added that the suspect’s home is “a very cluttered house,” saying Heuermann “was like a pack rat.”

Heuermann, 59, a married architect with offices in Midtown Manhattan, was arrested Thursday and charged with the 13-year-old slayings of three women whose bodies were found dumped in a marshy area near his home.

He was charged with murder in the deaths of Melissa Barthelemy, 24, Megan Waterman, 22, and Amber Costello, 27, whose remains were found in 2010.

He also is the prime suspect in the death of 25-year-old Maureen Brainard-Barnes, with the victims collectively known as the “Gilgo Four.” Their bodies were among 11 corpses found near each other at the Gilgo Beach site.

Cops have said they have collected a mountain of evidence at the accused killer’s house, including his distinctive Chevrolet Avalanche, a child-sized doll encased in wood and glass, a bookcase and a collection of rifles.

Heuermann, who has 92 gun permits, had a cache of weapons inside the house, police said.

The grisly murder cases tied to the architect remained dormant for years, until cops started to collect bits of evidence that led them to him.

Witnesses described a rare Chevy Avalanche vehicle near one crime scene, and Costello’s pimp provided police with a spot-on description of the 6-foot-4 accused killer.

DNA evidence found on a discarded pizza crust later proved crucial to tying him to the crimes, according to police.

Heuermann is being held without bail while police continue to search for evidence.