The NBA is investigating an incident in which Boston Celtics forward Antoine Walker pushed a fan.

NBA spokesman Tim Frank said Saturday that the league's security department is looking into the incident, which took place during the final minutes of Boston's home playoff loss to the New Jersey Nets on Friday night.

Walker was taken out of the game with 4:42 remaining and the Celtics trailing by 24 points in an eventual 94-76 loss. Responding to a fan heckling him from the row of seats directly behind the team's bench, Walker put his left hand on the right side of the fan's face and pushed him.

Friends of Walker's in the crowd descended upon the fan before the incident was broken up by security personnel.