A Southern California man was arrested Thursday night on suspicion of murder in connection with the disappearance of his neighbors, who were last seen at their home at a nudist ranch in San Bernardino County.

Michael Royce Sparks, 62, was booked and jailed in the disappearance of Daniel Menard, 79, and Stephanie Menard, 73, who were reported missing by a friend on Sunday and are now presumed dead, Carl Baker, the public information officer for the Redlands Police Department, told reporters Friday morning .

Baker told reporters later Friday that human remains had been found inside bags in a concrete bunker under Sparks home, KNBC-TV in Los Angeles reported . The remains have yet to be identified.

The Menards and their dog, Cuddles, who is also missing, were last seen Saturday at their home at Olive Dell Ranch, Redlands police said in an earlier news release. The couples unlocked car was parked across the street. Stephanie Menards purse and the couples cellphones were found inside their home, according to the Los Angeles Times .