Deputies first responded to the area between Quarry Road and Interstate 15, north of Stoddard Wells Road, after a motorcyclist reported locating possible skeletal remains on Monday around 10 a.m.
Coroner's investigators confirmed that the remains were human.
As detectives continued to investigate on Tuesday, authorities say they located more remains. There are two confirmed graves, where skeletal remains were found, and a third site was earlier suspected of being a grave, but Wednesday evening investigators said it was not.
The two confirmed grave sites are about 10 feet away from one another. The remains appeared to have been there for an extended period of time.
"It's hard to put a time frame on how long these bodies have been here," said Jodi Miller, spokesperson for the San Bernardino County Sheriff's Department.
The area was being excavated. Age and gender of the remains will be determined after an examination by a forensic anthropologist.
"It is very time-intensive, something that has to be done very slowly, very tediously, to ensure that any possible evidence is not destroyed while the remains are being excavated," said Miller.
In San Bernardino County, there are more than 700 unsolved missing-persons cases. Add to that the cases out of the surrounding counties, and investigators have their work cut out for them.
They will do DNA tests on the bones to see if they come up with a match, but that could take quite some time.
Anyone with information about the remains is urged to call (800) 78-CRIME.