(WJW) — Wendy’s is taking some precautions amid an E. coli outbreak across several states.

While no specific food as been confirmed to be source of the outbreak, the Centers for Disease Control and Prevention said many people reported eating sandwiches with romaine lettuce at Wendy’s locations in Ohio, Michigan and Pennsylvania before they got sick.

As a precaution, Wendy’s is removing romaine lettuce from its sandwiches in that region for the time being.

Health officials are working to determine if the romaine lettuce is the source of the outbreak and whether it was served or sold at other businesses.

Wendy’s released the following statement:

“We are fully cooperating with public health authorities on their ongoing investigation of the regional E. coli outbreak reported in certain midwestern states. 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.”

As of Friday, the CDC had reported 37 illnesses from the outbreak.

The Ohio Department of Health is also investigating the outbreak in that state, where there have been 19 reported illnesses. The CDC said the total number of sick people in this outbreak is likely higher than the number reported.

Symptoms of E. coli infections include diarrhea, a fever higher than 102 degrees, vomiting to the point of being unable to keep down liquids, and signs of dehydration.

If you are experiencing symptoms, the CDC asks that you keep a record of what you ate in the week before becoming sick in order to help identify the possible source of the infection.