(NewsNation) — Authorities say they have found more human remains at the home of a 62-year-old California man arrested last week in connection to the disappearance of a couple who went missing from a nudist community.

Investigators with the Redlands Police Department on Sunday were searching Michael Sparks’ property at the Olive Dell Ranch Nudist Resort for a fourth day when they found the additional remains.

NewsNation local affiliate KTLA reports authorities are working on identifying these remains, and it is unclear if they are from another victim or victims.

Officials believe the bodies of Stephanie Menard, 73, and her husband, Daniel, 79, are inside Sparks’ residence, said Carl Baker, a spokesperson for the Redlands Police Department.

The Menards were last seen Aug. 24 at their home inside the Olive Dell Ranch. They were reported missing the next day by a friend when they didn’t show up for church.

On Aug. 29, after authorities were tipped off about where the couple, who are presumed dead, were, they tried to locate Sparks. Police used a drone, then a battering ram, to tear through the house, KTLA wrote. 

Sparks was found underneath the house at Olive Dell Ranch, in a cement bunker where a cadaver dog alerted police to bags stuffed with human remains. He was arrested and charged with murder.

Another neighbor, Tammie Wilkerson, told NewsNation that she is staying at a hotel, and wants to move to another plot at the nudist resort after what happened.

“I hate (Sparks) because I’m traumatized now,” Wilkerson said. “We’re all traumatized.” 

NewsNation affiliate KTLA, NewsNation digital producer Cassie Buchman and The Associated Press contributed to this report.