Investigators expanded their search into Texas Monday for a 7-year-old girl who was reported missing after her mother was found dead in Oklahoma Sunday night. Authorities also are trying to find the dead woman's estranged husband, the Oklahoma State Bureau of Investigation said in a statement. The girl -- Aja Daniell Johnson -- was reported missing from Geronimo, Oklahoma, late Sunday, the bureau said. Her mother, Tonya Hobbs, 37, was found dead inside a parked RV Sunday night, the bureau said. Hobbs and her daughter were visiting Hobbsestranged husband, Lester William Hobbs, at his sister's home, the bureau said. Lester Hobbs, 46, and Aja are missing and are presumed to be in Hobbscar, said investigators who issued an Amber Alert to try to find her. Lester Hobbs is not Aja's biological father, police said. Texas authorities also issued an Amber Alert, Texas Department of Public Safety spokeswoman Lisa Block said. Authorities believe Hobbs has connections to Rockport, Texas, and the alert was issued preemptively, she said. Tonya Hobbs and her daughter were last seen Saturday night. Authorities did not say how Hobbs died, but the bureau said investigators believe someone killed her. The RV belonged to Lester Hobbs, and was parked at his relativeshome, Richard Goss, agent in charge of the state bureau of investigation's Lawton, Oklahoma, office, told reporters Monday.