A woman faces charges of child abuse and arson Tuesday after firefighters responding to a house fire in Santa Paula found her son with a plastic bag over his head and his hands tied in a bedroom by himself. Marical Magana, 47, was arrested after the fire was reported on Bahia Circle Sunday at about 6 p.m. Santa Paula police say a 911 call reported a structure fire with a woman tied to a bed and a young boy in another part of the home. Firefighters rescued Magana and her son and took them to Santa Paula Hospital to be treated for smoke inhalation. Santa Paula police says detectives determined she endangered her 3-year-old son by putting a plastic bag over his head and tying his hands before putting him in a bedroom by himself. Detectives were not able to determine a motive, police said.