FORT WORTH (CBSDFW.COM/AP) — Officials say one racing fan has died and another is in critical condition after being found suffering from carbon monoxide poisoning in their converted bus at the Texas Motor Speedway in Fort Worth.

The Tarrant County Medical Examiner’s Office on Monday identified the man who died as 49-year-old Cameron Hickman of Flower Mound. Hickman died Sunday at Texas Health Alliance Hospital in Fort Worth. A cause of death wasn’t immediately released.

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The bus was parked on the infield Sunday during NASCAR’s Texas 500. Bystanders reported two men were sick inside.

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Fort Worth Fire Department spokesman Kyle Clay says the bus had a gasoline-powered generator inside and it appears it was not properly ventilated. Clay on Monday had no information on the second critically ill man, who was flown to a hospital in Plano for hyperbaric treatment.

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)