Three-time NASCAR champion Tony Stewart has been hospitalized with a back injury and Stewart-Haas Racing is unsure of the extent of his injuries.

A team spokesman told The Associated Press that Stewart was injured in a non-racing accident on Sunday. He is being evaluated in an undisclosed hospital and able to move all extremities.

No further information was given and spokesman Mike Arning indicated Stewart's condition will not be updated again until Thursday.

Stewart is retiring at the end of this NASCAR season. He turns 45 in May and missed a third of the 2013 season with a broken leg he sustained in a sprint car accident.