Investigators searching a sprawling suburban Philadelphia farm in the disappearance of four young men who vanished last week discovered human remains, including the body of one of the men, the authorities announced early Thursday morning.

The announcement came hours after the authorities charged the son of the farm’s owners, Cosmo DiNardo, with stealing one of the men’s cars and trying to sell it for $500. Mr. DiNardo, 20, came under scrutiny early in the investigation and has been identified as a “person of interest” in their disappearance.

The remains were discovered in a 12.5-foot-deep “common grave” on the Bucks County farm, where local authorities, as well as an evidence response team from the Philadelphia office of the F.B.I., have brought in cadaver dogs, sifted through soil in rows of corn stalks, dug up concrete with a backhoe and surveyed the land on all-terrain vehicles.