At least 18 people were treated for minor injuries at Bowie yesterday in the aftermath of an incident apparently touched off by a loud noise just before the start of the feature race.

According to witnesses, a loud noise of an undetermined origin apparently caused several bystanders to begin shouting.

According to General Manager Al Karwacki, one man in a red sweater ran down a flight of steps and threw a chair through the plate glass window in the grandstand that serves to protect the fans from the elements and jumped to the ground about 15 feet below.

Clusters of fans were reported by the track security as running toward exits, some asking as they ran if there was a fire.

Karwacki said, "We don't know what started the panic. When the man in the red sweater threw that chair through the glass, everybody appeared to become frightened and began to run."

The episode began as the horses were being loaded into the gate for the running of the John B. Campbell Handicap, Bowie's richest race. Eighteen people were treated at the track first aid station by the physician in attendance, Elwood LaBrosse, who sent seven people to area hospitals for observation. All later were released.

Dr. La Brosse said that none appeared to be seriously injured. "It was mostly bruises and sprains, and some were just plain scared," he said.

The man in the red sweater never was identified. Clubhouse elevator operator Kathy Heisler said, "I have never seen anything like it. People tried to jam in here and scared the daylights out of me. They kept yelling there's a fire or somebody with a gun and they demanded that I take them down."

Karwacki said director of security William Ramsey will be in charge of a special task force to investigate the incident.