The Centers for Disease Control and Prevention said on Friday that romaine lettuce may have been the cause of the outbreak.

Most of the people who got sick had eaten sandwiches at Wendy's in the week before they got sick. The C.D.C. said that 22 people said they had eaten at a Wendy's restaurant.

37 people have become ill and 11 of them haven't been interviewed. There have been no deaths.

The company and C.D.C. said that the lettuce used on the sandwiches is different from what is used in the salads.

Wendy's said it was cooperating with public health authorities on their investigation of the E coli outbreak. The C.D.C. has not yet confirmed a specific food as the source of that outbreak, so we are taking the precautionary measure of removing the sandwich lettuce from restaurants in that region.

People shouldn't avoid eating at Wendy's or buying lettuce, according to health officials.

According to the C.D.C., there is no evidence that romaine lettuce sold in grocery stores, served in other restaurants or in people's homes is related to the outbreak.

The agency said that 29 people had been sick in the outbreak. At least eight more people had been affected.

There were 19 cases of hemolytic uremic syndrome reported in Ohio and fifteen in Michigan. There were cases in Pennsylvania and Indiana. 10 people are hospitalized according to the C.D.C.

According to the C.D.C., the infections of people and animals can start when someone ingests food contaminated with feces.

Health officials said that the symptoms of E. coli usually start about three to four days after ingestion. People are encouraged to contact their health care provider if they experience symptoms even if they don't recover from the disease.

The C.D.C. said 167 people were affected by the E. coli outbreak. There were no deaths but 85 people were hospitalized with various illnesses.

Lab testing and data analysis show that those cases were caused by the same strain of E. coli that caused the romaine lettuce outbreak.