Boys riding off-road motorcycles discovered skeletal human remains in the Riverside County town of Cherry Valley.

The Riverside County Sheriff's Department said in a statement that deputies from the Cabazon Station were led by the boys to the hilly, rural area Sunday, where the deputies found a human skull and other skeletal remains.

Authorities say a preliminary investigation failed to reveal the person's age, sex or cause of death.

The statement says there has been extensive animal activity around the body and it appears it has been there for a very long time.

Darkness fell quickly after the body was discovered and only part of the area was searched. Investigators will return to the scene Monday.