A 10th person found in the back of a sweltering tractor-trailer in Texas on Sunday has died after being taken to a hospital, the San Antonio Express-News reported. Eight male immigrants were found dead in the trailer when officials arrived and a ninth person died at the hospital later that day. Police said the victims are believed to have died as a result of heat exposure or asphyxiation. Nearly 20 other people found in the trailer were taken to the hospital in critical condition. Officials are investigating the tragedy as a human-trafficking case.