MASSAPEQUA PARK, N.Y. (NEWSnet/AP) — Investigators have been digging in the yard at the Long Island home of Rex Heuermann, who is charged with killing at least three women and burying their remains on a beach highway.

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

During the weekend, police dismantled a wooden deck at the house. The porch has been replaced by a white tent, with a state medical examiner’s truck parked nearby.

Investigators with shovels scraped through the upturned earth in Heuermann’s yard.

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.

Authorites have collected more than 100 firearms from the house 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.

The July 14 arrest of Heuermann, 59, marked a breakthrough in the cold case that first drew headlines in 2010, when police began searching for a missing woman, Shannon Gilbert, near Long Island’s Gilgo Beach. Authorities found 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, Maureen Brainard-Barnes.

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

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