VICTORVILLE >> Sheriff’s investigators unearthed the remains of four people Wednesday from two shallow graves discovered on the outskirts of the city, officials confirmed.

Sheriff’s investigators completed their three-day, 30-hour crime scene investigation by nightfall Wednesday, San Bernardino County sheriff’s spokeswoman Jodi Miller said.

“It is difficult at this point to state how long it will take to determine the causes of death,” she said.

A forensic anthropologist will assist in the autopsies to determine age, gender and cause of death, but it is unknown when the autopsies will be conducted, she said.

Earlier Wednesday, two workers could be seen digging into an approximately 10-foot-by-10-foot area in High Desert scrubland while additional personnel stood nearby sifting through dirt for bones and other evidence.

“This is an active and ongoing investigation,” Miller said at that time. “It appears the remains have been there for an extended period of time.”

An off-road motorcyclist on Monday found the first set of remains and reported it to the Sheriff’s Department, authorities said in a statement.

Deputies returned on Tuesday and made the grim discovery of the remains of more than one person between Quarry Road and the 15 Freeway, north of Stoddard Wells Road.

The area sits west of the 15 Freeway and consists of small rolling hills. There are no homes or businesses nearby.

Although the skeletal remains were unearthed on the outskirts of Victorville, City Manager Doug Robertson said the news still was stunning.

“It certainly is shocking,” Robertson said Wednesday. “I’m more curious about what the Sheriff’s Department is able to determine as to how old they (the skeletal remains) are.”

Anyone with information may call sheriff’s Detective Armando Avila at 909-387-3589 or anonymously at WeTip, 800-78-CRIME, or leave information on the WeTip hotline at www.wetip.com.

Staff Writer Sandra Emerson contributed to this report.