If you saw the during Saturday’s NASCAR Xfinity Series race and guessed tire failure was the culprit, congratulate yourself. There was immense confusion about the cause of the incident, and for good reason—it was no ordinary tire failure.

The explosion happened to the No. 70 car of Derrike Cope during the Zippo 200 at Watkins Glen International, taking the driver out of contention with 23 laps to go and perplexing the NASCAR community—crew chiefs, car chiefs, drivers and the like. Cope was fine, but NASCAR decided to impound the car for a trip back to its research and development center for further evaluation.

Technical inspectors deemed the plume of smoke that rose during the incident, which can be seen below, to be brake dust rather than anything related to a fire, according to . The sanctioning body’s vice president of officiating and technical inspection, Elton Sawyer, said the right-front tire degraded due to excess heat from a broken spindle.

The part where this tire failure gets weird is when it happened, according to the assessment by Sawyer and his team. Tires usually pop while drivers are at full speed, leading to a quick failure. Cope slowed down and pulled off of the track upon reaching Watkins Glen’s “bus stop” turn, reducing airflow to the tire and creating a weird explosion that was, evidently, a bit foreign to NASCAR.

From USA Today:

The sidewall of the tire subsequently weakened and when Cope pulled off course, air flow was impeded and allowed the still-inflate tire to, in essence, roast.

“So he lost a bead, then basically you’ve got all the fabric in the side wall that is starting to deteriorate and as soon as the vehicle came to a stop you’ve got all that radiant heat that’s basically just sitting there, the soft point of the side wall is where it basically explodes,” Sawyer said.

According to USA Today, NASCAR returned the mangled car to Cope following their evaluation of it. The burden of avoiding this type of failure won’t be on Cope and his team going forward, though—Sawyer said the situation is “not something [NASCAR will] sweep under the rug.”