Police have smashed into a Southern California home and arrest the neighbour of a couple living in a nudist resort who were reported missing.

Officials believe the bodies of Stephanie Menard, 73, and her husband, Daniel, 79, are inside the residence, though they first have to shore up the home to make it safe to search, said Carl Baker, spokesman for the Redlands Police Department.

“We are confident that they are deceased and that they are still here on the property,” Baker said on Friday.

He did not release any information about a possible motive.

Officials later said searchers had found human remains in bags in a concrete bunker under the home.

The remains were not immediately identified.

Michael Royce Sparks, 62, was booked into jail on suspicion of homicide on Thursday night after being found under his home at Olive Dell Ranch, which is described as a residential RV park and family-friendly nudist resort on its website.

He was ineligible for bail and is scheduled for a Tuesday court appearance.

A dog trained to find cadavers indicated at least one body was under the house, Baker said at a news conference.

A friend reported the couple missing on Sunday and said they were last seen at their home on Saturday morning.

Their pet dog, a shih tzu named Cuddles, was also missing.

The couple’s unlocked car was found later on Sunday, not far from their residence, and both their phones, along with Stephanie Menard’s purse, were still inside their home.

Daniel Menard was described as a diabetic with dementia.

Tammie Wilkerson, a friend of the couple, told KABC-TV that the Menards were kind people involved in the community.

“They’re very sweet people,” Wilkerson said. “There’s not a mean bone in their body at all, which makes this very confusing.”

The arrest followed rapid developments that began when police were at the park on Thursday to search the area and knock on doors.

“We received information from a source that a person who was involved in their disappearance was here on the property,” Baker said.

Police went to the suspect’s home but attempts to contact him were unsuccessful and a tanklike tactical vehicle was brought in, Baker said.

The suspect was arrested after surrendering voluntarily, Baker said.

-AAP