Things keep getting worse for Chipotle Mexican Grill.

An Ohio man sued Chipotle on Tuesday as state health officials investigate a "possible foodborne illness outbreak" stemming from one of the burrito chain's locations in Powell, Ohio, according to the lawsuit obtained by CNBC. Local health officials have received more than 500 calls so far — reporting nausea, diarrhea and fever, among other symptoms, after eating at the restaurant.

Plaintiff Filip Syzller is asking for $25,000 after he purchased three chicken tacos on July 29 from Chipotle and then started experiencing nausea, headaches and hot flashes, according to the lawsuit filed in Delaware County in Ohio. He was undergoing medical treatment, the lawsuit says.

"The health and safety of our customers and employees is our number one priority," Chipotle said in a statement to CNBC when asked for a comment on the suit. "We have been working with local officials to investigate and will continue to do so."

The company had told CNBC on Tuesday morning that the local health department received just two illness complaints. On Wednesday, the Delaware General Health District said it received 518 inquiries related to the outbreak and had delivered 33 stool sample kits to people who reported they were ill.