COLUMBUS, Ohio (WCMH) — An E. coli outbreak sickening people in Ohio may have something to do with an ingredient at a fast food chain.

Ohio has seen 19 people infected with E. coli O157 at the last update on Aug. 17, the Centers for Disease Control and Prevention said. In total, 37 people have confirmed infections and nine of them have been hospitalized. Three developed kidney failure from the bacteria, but no one has died.

The CDC said that it has not yet confirmed a specific food as the source of the infections, but 22 patients, including in Ohio, told the health agency that they ate a Wendy’s sandwich with romaine lettuce the week before getting sick.

Wendy’s gave NBC4 this statement after the CDC mentioned the chain.

“We are fully cooperating with public health authorities on their ongoing investigation of the regional E. coli outbreak reported in certain midwestern states,” a Wendy’s spokesperson said in a statement. “While the CDC has not yet confirmed a specific food as the source of that outbreak, we are taking the precaution of removing the sandwich lettuce from restaurants in that region. The lettuce that we use in our salads is different, and is not affected by this action.”

The CDC said it is not advising people to avoid eating at the restaurant. It also did not warn people to avoid romaine lettuce altogether.

“At this time, there is no evidence to indicate that romaine lettuce sold in grocery stores, served in other restaurants, or in people’s homes is linked to this outbreak,” a CDC spokesperson said.

CDC investigators are working now to confirm if romaine lettuce is the source of the E. coli outbreak. It’s also investigating if the lettuce served at Wendy’s was at any other business or restaurant.

Local infectious disease specialist Dr. Joseph Gastaldo wants to be sure people are aware of E. coli symptoms, the first sign of which will be unusual abdominal pain after consuming the bacteria.

“It’s really dependent on the type of E. coli you get infected with, but with our current outbreak, if people do get an E. coli infection related to lettuce or other types of produce, symptoms usually begin within two or three days,” Gastaldo said.

Call your healthcare provider if you develop severe E. coli symptoms. View more details and symptoms from the CDC here.