SAN ANTONIO (AP) — A 60-year-old man who was arrested after authorities say at least nine people died in the back of a sweltering tractor-trailer found outside a Walmart in San Antonio is due in federal court.

Federal prosecutors say James Mathew Bradley Jr. of Clearwater, Florida, will be charged on Monday.

U.S. Immigration and Customs Enforcement acting Director Thomas Homan says the truck driver is in custody, but the local U.S. Attorney's Office wouldn't say whether Bradley was the alleged driver who was arrested.

Officials say nearly 20 other people rescued from the back of the rig early Sunday were hospitalized in dire condition, many with extreme dehydration and heatstroke.

Foreign officials from Mexico and Guatemala confirmed people from those countries were found in the abandoned tractor-trailer.