In short:

The family of NASCAR driver Kyle Busch has confirmed his death was caused by severe pneumonia that turned into sepsis.

Busch, 41, died this week in hospital just days after racing.

Considered one of the best drivers in NASCAR's histroy, Busch was Cup series champion in 2015 and 2019.

NASCAR driver Kyle Busch died from severe pneumonia that turned into sepsis, according to a statement provided by his family. 

"The medical evaluation provided to the Busch Family concluded that severe pneumonia progressed into sepsis, resulting in rapid and overwhelming associated complications," said the family statement, which was released on Saturday, local time.

"The Family asks for continued understanding and privacy during this difficult time."

Dakota Hunter, vice-president of Kyle Busch Companies, said the family received the medical evaluation on Saturday.

Busch, a two-time NASCAR Cup Series champion considered one of the best drivers of all time, died Thursday. He was 41.

The Busch family, Richard Childress Racing and NASCAR confirmed his death hours after announcing that Busch had been hospitalised this week and would miss Sunday's Coca-Cola 600 at Charlotte Motor Speedway.

Busch experienced shortness of breath and was coughing up blood the day before his death, according to a 911 call obtained on Friday by USA Today.

He is survived by his wife Samantha, 11-year-old son Brexton and 4-year-old daughter Lennix. He was the younger brother of NASCAR Hall of Fame member Kurt Busch, 47.

Busch accrued 234 wins across NASCAR's top three series: 63 in the Cup Series, 102 in the O'Reilly Auto Parts Series and 69 in the Craftsman Truck Series. He won the trucks race at Dover last Friday, six days before his death.

The Las Vegas native was the NASCAR Cup Series champion in 2015 and 2019. He never won the Daytona 500 but claimed the pole for the first time this year before finishing 15th.

Among Busch's big wins were the 2008 Southern 500, the 2015 and 2016 Brickyard 400 and the 2019 Coca-Cola 600.

Reuters