SAN ANTONIO – Early Sunday morning, police arrived at a southwest-side Walmart to find a semi-truck filled with several people in various stages of medical distress.

Emergency responders found dozens of people in distress inside a hot semi-trailer located at a Walmart in southwest San Antonio around 12:30 a.m. Police said there was a total of 38 victims found in and around the trailer after an employee of the store notified authorities.

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Of the 38 victims, eight were pronounced dead at the scene. Officials said all of the deceased are believed to have died as a result of heat exposure/asphyxiation. Their bodies were taken to the Bexar County Medical Examiner's Office for examination where a cause of death will be determined.

Seventeen of the victims had life-threatening injuries and were taken to University Hospital and San Antonio Military Medical Center. Thirteen of the victims had non-life threatening injuries and were taken to five other area hospitals.

WATCH: Scene at San Antonio Walmart

At early light, the police helicopter returned to search the undeveloped land near the shopping center in an attempt to locate any additional victims who may have left the scene.

Homeland Security is leading the criminal investigation. The driver taken into federal custody faces both state and federal charges.

WATCH: Sue Calberg breaks down video from scene

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