“We were kind of all riding as a group,” Biffle told Sirius XM Radio on Wednesday, via USA Today Sports. “We started kind of hearing bits and pieces that he hurt his back. That’s all we knew.”

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Biffle said he “wasn’t near what went on” and didn’t see the accident but knew Stewart received aid quickly.

Stewart, 44, had to be airlifted to a hospital, where he was treated for a burst fracture of his L1 vertebra. He underwent back surgery Wednesday and will miss the Daytona 500 later this month, Stewart-Haas Racing said Thursday. He’s expected to make a full recovery.

“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 said.

Biffle said the dunes can be “unpredictable.”

“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.”