While Boston coach Jim O'Brien didn't want to take any chances when a gagging gas was released behind his team's bench against the Los Angeles Clippers, NBA officials - working with Boston police and FleetCenter security - decided that the substance sickening the players and the fans sitting behind them was most likely Mace or pepper spray released as a prank.

"It is a sick prank," FleetCenter chief Richard Krezwick said yesterday. "In this day and age, people like that have to be punished."

"With what's going on in the world, we're obviously going to be very cautious," Celtics forward Antoine Walker said. O'Brien, asked whether he was concerned the fumes might be related to an attack, said, "Of course."