The search for the body of a 6-year-old Apple Valley boy continued for a second day Tuesday as his mother and her twin sister pleaded not guilty to murder charges. Duke Flores’ mother, 29-year-old Jackee Racquel Contreras, and his aunt, Jennifer Rachel Contreras, entered the plea at the Victorville Superior Court. The San Bernardino County District Attorney’s Office announced the charges on Monday, when detectives and volunteers began looking through 1,200 tons of waste at the Victorville Landfill. The scope of the search spans a 70-by-70 foot area that’s about 10 feet deep, according to the county Sheriff’s Department. “Following investigative leads, detectives believe that Duke was placed in a dumpster,” the agency said. Investigators have not disclosed further details about what led them to believe the child was killed. Tuesday’s search efforts ended around 5 p.m. with no remains discovered. Crews planned to return to the landfill Wednesday morning. Apple Valley police learned the boy was missing last Thursday after conducting a welfare check requested by a family member, according to the Sheriff’s Department. Jackee Contreras told officers her son had not been seen in over a week, authorities said. Police took her into custody for not reporting his disappearance. The next evening, family members held a vigil and pleaded for anyone who knows about the boy’s whereabouts to come forward. On Saturday, authorities booked Jackie Contreras on suspicion of murder, as well as her sister. Tuesday’s search started at 8 a.m. and involved homicide detectives, 19 Sheriff’s Department volunteers, two canines, 17 additional agency employees and landfill personnel. Anyone with information can call Detective Narcie Sousa at 909-387-3589 or sheriff’s dispatch at 909-387-8313. Those who wish to remain anonymous can contact the WeTip hotline at 800-78-CRIME or visit wetip.com.