Jeff Gluck

USA TODAY Sports

Greg Biffle was among a group riding with Tony Stewart in the sand dunes of Southern California when Stewart suffered a back injury on Sunday, he told SiriusXM's NASCAR channel on Wednesday night.

Stewart-Haas Racing said Tuesday the driver/owner was hospitalized with an injury following an off-road vehicle incident. Biffle confirmed to Sirius he was in Stewart's group, though he "wasn't near what went on" and didn't see exactly what happened.

"We were kind of all riding as a group," Biffle told Sirius. "We started kind of hearing bits and pieces that he hurt his back. That's all we knew.

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"I do know the people that helped him ... (said) he was walking and moving all of his extremities, but he was in a lot of pain."

Biffle frequently rides sand cars in the famed Glamis dunes and has his own building there. He called the dunes "unpredictable" and said it's possible to "land harder on some spots than others."

"I've knocked the wind out of myself, I've thought I'd broken my tailbone or back before," he said. "Things can happen. I don't know exactly what happened (to Stewart), but it can be done."

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SHR said an update on Stewart's condition will be given Thursday. The team has not said whether he will miss the Daytona 500 or any other race in what is scheduled to be his final Sprint Cup season before retirement, but NASCAR CEO Brian France issued a statement Tuesday saying he would "look forward to seeing (Stewart) back in our sport when he's ready to return."

Sand cars are high-powered machines that tear through the sand and can race up dunes that are many stories tall. Drivers can jump the dunes at speed, catch some air and land in sand on the other side.

Follow Jeff Gluck on Twitter @jeff_gluck.

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