BRUNSWICK, Maine (AP) -- A once-benign tradition that started with Bowdoin College hockey fans tossing tennis balls onto the ice has turned ugly. Consequently, future games may have to be played in an empty arena. The tennis balls have given way to grilled cheese sandwiches, coins and a steer's head, all of which have come raining down onto the Dayton Arena ice. The college now says enough is enough. Earlier this week, police ejected about 100 fans after grilled cheese sandwiches -- symbolizing that the goalie had been burned -- came sailing onto the ice during a game against Colby. Bowdoin won 6-1. Students had been warned before Tuesday night's game that they would be tossed out, and their student identification cards confiscated, if anything other than a puck was seen moving across the ice. Flyers signed by Bowdoin coach Terry Meagher and team captain Tim O'Sullivan also warned that subsequent offenses would lead to the ejection of all fans -- even if that means games must be completed without an audience. "It's been going on for years and years and years, but it's not going to go on anymore," said Bowdoin spokesman Scott Hood. Students at Colby College last year tossed the head of a steer on the ice when it was clear the home team wasn't going to overcome a 1-0 deficit in the final seconds of the game. Play was stopped for nearly half an hour. "It was red and bloody, but it wasn't dripping," said Craig Cheslog, Bowdoin's sports information director. The Bowdoin-Colby hockey rivalry is one of several between colleges in the Northeast in which fans have grown accustomed to tossing things on the ice. But Cheslog said the tradition isn't very funny for players who hit thrown objects. "If a skater runs over a thing like that, the next thing you know, you've got a torn knee or a blown ankle," he said.