Hawaii News Now reports that at least 29 people have reported falling ill after dining at popular upscale Waikiki eatery Herringbone this week, the state Health Department said.

Health officials say they’re investigating a “possible norovirus issue.”

The Health Department got its first report of illness from a diner on Monday.

That person had dined at the restaurant over the weekend. Five people in the diner’s party had become ill, the Health Department said.

Officials then received several other reports from other patrons of the restaurant. All have recovered after one to two days of being ill.

Herringbone, located at the International Market Place, shuttered its doors on Thursday following a report of possible food poisoning.

Originally, the Health Department said three customers got sick Saturday after sharing a tossed salad.

But customers told Hawaii News Now that more than three people got sick and didn’t eat any salad.

In a statement, Herringbone said it was “working closely with the Health Department to investigate this matter and look forward to reopening as soon as possible.”

Noroviruses are a group of viruses that cause what’s commonly known as the stomach flu.

Symptoms usually begin 24 to 48 hours after exposure, and include nausea, vomiting, diarrhea and stomach cramps.