CARSON, Calif. (KABC) -- The Los Angeles County Sheriff's Department is searching for a foster child, believed to have been taken by his biological mother.Authorities said 8-year-old Dylan Kostenko was picked up from school by his biological mother, Dariia, who is only allowed supervised visits.Surveillance video shows Dariia walking Dylan away from Towne Elementary School in Carson just after 2:30 p.m. Tuesday.Dylan was last seen wearing blue jean shorts and a black T-shirt with a picture of a dog, and the phrase "dab all day." Dariia was last seen wearing a red hooded sweatshirt.Dariia is known to frequent the West Los Angeles area, but also has family in New York. Anyone with information is asked to contact the Carson Sheriff's Station at 310-830-1123.