Authorities began digging with a backhoe in the backyard of Rex Heuermann’s Massapequa Park home late Sunday afternoon.

Earlier in the day, News 12 was on the scene when a K-9 and a ground-penetrating radar machine was brought in.

LIVE BLOG: Gilgo Beach Murders

Heuermann has been charged with first- and second-degree murder in connection to three Gilgo victims: Melissa Barthelemy, Megan Waterman and Amber Costello. He’s the prime suspect in a fourth death. He pleaded not guilty last week and is due back in court Aug. 1.

Detectives are trying to determine if any of the killings occurred at the Massapequa Park home. Chopper 12 was above the scene on Saturday where investigators were combing through the property.

The deaths of 11 people whose remains were found in 2010 and 2011 have long stumped investigators. Most of the victims were young women who had been sex workers. Several of the bodies were found near Gilgo Beach.

Suffolk police confirmed last week that investigators are looking into possible connections between Heuermann, and unsolved cases around the nation – including South Carolina, Nevada and Atlantic City, where four women were murdered in 2006.

Neighbors are still trying to process what has unfolded before their eyes over the past week since the architect and father of two was taken into custody in New York City. They say the addition of a police dog on scene and ground penetrating radar has them fearing the worst.

"For them to actually find, maybe remains in his backyard – that’s really, really shocking,” said one neighbor.

Investigators have not revealed what, if anything, they have found at the house over the weekend. According to neighbors, Heuermann lived on 1st Avenue in Massapequa Park his entire life.

Since his arrest, investigators have also searched two storage units in connection with the case.

News 12 was told Saturday that the investigation is expected to wrap up this week. 

WATCH: DOCUMENTARY AND BACKGROUND INFORMATION - Gilgo Beach: Unsolved