Authorities have found the vehicle belonging to an Arizona mother who has refused to say where her 8-month-old son is.

FBI spokesman Eric Vasys says San Antonio police and FBI agents found the vehicle outside a San Antonio motel Tuesday night and are processing the car for evidence that might point to the whereabouts of 8-month-old Gabriel Johnson. There were no obvious signs of violence.

Johnson's mother, 23-year-old Elizabeth Johnson, was arrested in Miami Beach, Fla., last week after she failed to appear for a custodial hearing in Phoenix. The baby's father told authorities the mother had threatened the child.

She has refused to say where the baby is.