The search for the body of a missing boy believed to be in a Victorville landfill was suspended again Wednesday with no remains found, officials said.

Crews are expected to resume their efforts at the landfill to recover the body of 6-year-old Duke Flores of Apple Valley for a fourth day Thursday morning, the San Bernardino County’s Sheriff’s Department said in a news release.

Flores’ mother, 29-year-old Jackee Racquel Contreras, and her twin, Jennifer Rachel Contreras, were arrested Saturday, two days after a family member requested police perform a welfare check on the boy. They’ve since been charged with murder, and both pleaded not guilty.

Jackee allegedly told officials her son hadn’t been seen for more than a week, and after interviewing her further investigators identified her and her twin as homicide suspects in the case.

Other family members said the boy, who has autism, has wandered away in the past.

Detectives have yet to reveal what evidence ties the sisters to the boy’s disappearance and presumed death. However, they believe he was killed and placed into a dumpster.

Investigators have centered their search on a 70-feet-square, 10-feet-deep plot of the landfill, sifting through about 1,200 tons of material.

Wednesday’s efforts involved homicide detectives, 16 volunteers and 12 other staff members from the Sheriff’s Department, three search dogs and landfill personnel.

Both sisters are being held without bail.

Anyone with information can contact Detective Narcie Sousa at 909-387-3589 or Sheriff’s dispatch at 909-387-8313. Those who wish to remain anonymous can submit a tip via 800-782-7463 or wetip.com.