Investigators have been digging in the yard at the Long Island home of Rex Heuermann, who was charged earlier this month with killing at least three women and burying their remains on a remote stretch of beach highway.

A yellow excavator that had been seen scooping dirt in the backyard Sunday was still at the house Monday. In Associated Press drone footage, a man could also be seen operating a piece of equipment that can be used to scan for buried objects.

Over the weekend, police dismantled a wooden deck at the house.

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“They yelled ‘lift’ and brought it up in one big piece, as if it was a cover,” a neighbor, Barry Auslander told the AP.

The porch has been replaced by a white tent, with a state medical examiner’s truck parked nearby.

Investigators with shovels could be seen scraping through the freshly upturned earth.

Investigators are trying to determine whether any of the killings happened inside the Massapequa Park home that Heuermann shared with his wife and two children.

Suffolk County Police Commissioner Rodney Harrison told reporters at the scene that authorities were doing a “total investigation around the house to see if there is anything out there that we need to take a closer look at.”

He declined to detail what evidence might have been recovered, but confirmed that police had found a vault in which Heuermann stored numerous guns.

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Authorites have pulled more than 100 firearms from the house, along with a large doll encased in glass and a portrait of a woman with a bruise on her face. Police also got a warrant to conduct searches of Heuermann’s property in South Carolina.

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The July 14th arrest of Heuermann, a 59-year-old architect, marked a stunning breakthrough in the long-stalled cold case that first drew headlines in 2010, when police began searching for a missing woman, Shannan Gilbert, near Long Island’s Gilgo Beach.

Instead, they discovered 10 sets of human remains scattered along a long barrier island. The dead included eight women, one man and a young child.

Heuermann, who has pleaded not guilty, was charged with killing three of the women – Melissa Barthelemy, Amber Costello, and Megan Waterman. He is the prime suspect in the death of a fourth woman, Maureen Brainard-Barnes.

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The bodies of the four women were found along the same quarter-mile (0.4-kilometer) stretch of Ocean Parkway. Heuermann has not been accused in connection to the other remains, and police have suggested the deaths may be the work of multiple killers.

In South Carolina, where Heuermann’s brother lives, police are seeking video recordings and writings related to the killings, burlap, duct tape, guns and ammunition, cutting tools, and a specific type of paper towel from the Bounty Modern Print Collection.

Authorities also seized a Chevrolet Avalanche, which Heuermann had transferred to his brother in 2012, from the property. The vehicle was spotted by a roommate of one of the victims shortly before her disappearance, a tip that ultimately proved crucial in helping police make an arrest.