The Princeton Health Department received 30 reports between Thanksgiving and Tuesday of individuals experiencing gastrointestinal illnesses.

All 30 people ate at the restaurant at the Nassau Inn on Thanksgiving or the day after the holiday, Princeton Health Officer Jeffrey Grosser said. Many of the people also ate at other restaurants during the time period.

The health department has increased its surveillance of retail food establishments because of the incidents, and the Nassau Inn was inspected yesterday.

Laboratory testing has not yet confirmed the cause of the illnesses yet, but Grosser said the Norovirus is suspected in most or all of reported cases because of the symptoms and the time frame for the onset of symptoms and the recovery. The Norovirus is the most common cause of gastrointestinal illness and is especially common during the winter months.

“All the phone calls we received were similar in terms of where people ate, when people became ill (Thursday and Friday) and when they started feeling better (Sunday and Monday),” Grosser said.

An inspection of the restaurant at the hotel only revealed minor issues that can easily be rectified. Grosser said the issues did not cause the illnesses. About 70 percent of all Norovirus outbreaks are spread by food workers.