Several clues point to the highly contagious norovirus as the mystery culprit that may have sickened more than 100 weekend guests at the Swan Club, leading county health officials to shut it down temporarily, the Roslyn catering hall’s owner said.

The Swan Club, which has been around for decades, has served as the backdrop to many GOP dinners and fundraisers, and owner Bobby Sidana worries the outbreak has damaged his business’ reputation. He received 300 calls Wednesday, most of them customers who support him.

He said he contacted health officials Monday as soon as guests notified him about gastrointestinal problems. The health department has ordered his staff to undergo tests, including for norovirus, he said, and will be looking at the facilities of the club’s food purveyors.

“We said just come in and do a full inspection here,” Sidana said. “We don’t want to take a chance with safety.”