ASHBURN, Va. (AP) - The NFL says a 30-yard touchdown run by Carolina Panthers running back DeAngelo Williams should not have counted because of an inadvertent whistle.

The league said Monday that the Panthers should have instead been offered the ball at the 17-yard line - at the point where line judge Thomas Symonette blew his whistle and mistakenly thought Williams had stepped out of bounds. Carolina could've also chosen to replay the down at the 30.

Williams kept going and was awarded the first-half touchdown in the Panthers' 21-13 victory Sunday. Redskins linebacker Perry Riley said he stopped pursuing the play because he heard the whistle.

Referee Carl Cheffers said after the game that the officials decided the whistle wasn't blown until Williams reached the end zone and didn't affect the play's outcome.