"On a play from scrimmage, if an offensive player fumbles anywhere on the field during fourth down, only the fumbling player is permitted to recover and/or advance the ball. If any player fumbles after the two-minute warning in a half, only the fumbling player is permitted to recover and/or advance the ball. If recovered by any other offensive player, the ball is dead at the spot [ie, down] of the fumble unless it is recovered behind the spot of the fumble. In that case, the ball is dead at the spot of recovery.
Any defensive player may recover and/or advance any fumble at any time."