The restaurant reopened on Monday after closing for 72 hours for a deep cleaning and to remove all of the food, said investigators.
Bryan Clayton, the man filing the lawsuit, ate food from Federico's Mexican Restaurant located at 13132 W. Camelback Road on July 27 and July 29, the law firm Marler Clark wrote in a news release.
The Maricopa County Department of Public Health announced Monday there are now 30 reported cases in a bloody diarrhea outbreak with 12 people hospitalized.
Health officials initially announced Friday that 11 of the 15 people affected reported eating at the restaurant, but now say all of the victims confirmed eating at the restaurant.
Laboratory results indicated the bacteria causing the illness is E. coli O157, but samples of the food tested days later by health investigators found no traces of the bacteria; which is not uncommon, they said.
Clayton started experiencing abdominal cramps and diarrhea on July 30 and sought medical care the next day, the news release said. He was treated for dehydration in the emergency room and was released on Aug. 1.
The law firm said Clayton experienced worse symptoms soon after and was admitted to West Valley Hospital in Goodyear where he remains hospitalized.
This is the only Federico's location that is under investigation.
Susie Delgado was one of the first customers to return to the restaurant when it opened its doors on Monday.
"I have five of my seven grandchildren here eating," she told ABC15. "If I thought it was bad, I would not bring my grandchildren."