INDIANAPOLIS -- The number of people reporting to health officials that they became ill after eating at an Indianapolis restaurant reached 165 Thursday, up from 19 a day earlier, Marion County Health Department spokesman John Althardt said.

The ill told health officials that they had recently eaten at the Olive Garden restaurant in the Castleton area. Many of the sick reported eating there between Saturday and Monday and coming down with classic symptoms of food-borne illness -- including vomiting, diarrhea, nausea and fever -- by Tuesday, 6News' Stacia Matthews reported.

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MCHD officials began an investigation Tuesday, inspecting the restaurant and reviewing its food-handling procedures. On Wednesday, the department's Ed Culver said the restaurant took follow-up measures and said it was safe to eat there now.

The department said it believes a few Olive Garden employees had come to work while ill, including one who had flu-like symptoms. In all, six employees called in sick on Monday. But it said it still is trying to determine what caused the customers' illnesses.

Investigators have been recording what the ill ate and collecting stool samples for analysis.

"It sometimes can take a couple of weeks," Culver said of the investigation. "We may have something before that, but I can't guarantee that."

One of the ill, Heather Burdette, told 6News that she and six other people she knew became sick after they dined with her at the restaurant. She said Thursday that she still can't hold down any food.

"I don’t want to eat anything," Burdette said. "The nausea comes and goes."

Health officials said most of the illnesses are resolved themselves within 36 hours.

Because some of the sick are residents of Hamilton County, the health department in that county also is investigating.

Health officials asked that anyone who became ill after eating at the restaurant should contact the Marion County Health Department at 317-221-2222 or the Hamilton County Health Department at 317-776-8500.