DAYTONA BEACH, Fla. — NASCAR is placing drivers Kurt Busch and Tony Stewart on probation for six races, beginning with Sunday's Daytona 500.

The punishment follows a confrontation between the two former series champions, who wrecked in practice last week and then carried it into the NASCAR officials' trailer.

NASCAR says the probation stems solely from the on-track portion of their clash, when the drivers deliberately used their cars as battering rams.