GRAND RAPIDS, Mich. (WOOD) — As federal health officials investigate a possible link between a multistate E. coli outbreak and lettuce served on sandwiches at some Wendy’s franchises, the number of cases in Michigan continues to grow.

Michigan had a total of 45 cases as of Monday. Ten of those are in Kent County, which has the most of any county in the state. Ottawa County has six cases and there is one case in each of Muskegon, Allegan, and Branch counties.

Cathy Armstrong with the Kent County Health Department said the numbers are expected to increase.

“We have gotten some cases towards the end of last week so we don’t believe that it’s completely over yet,” Armstrong said.

Some of the patients are children who are being treated at Helen DeVos Children’s Hospital in Grand Rapids. Dr. Kira Sieplinga said the bacteria can be especially serious for children.

“We’ve seen several cases of children who have had acute kidney complications due to E. coli infections,” Sieplinga said. “The strain that we are seeing during this outbreak can be more severe in children who are less than 10.”

Health departments are sending food samples to be tested. One Wendy’s location in the Hudsonville area temporarily closed to address health code violations not related to lettuce. It is now back open, according to Ottawa County Department of Public Health spokesperson Alison Clark. The department investigated after receiving reports of illness from people who had eaten there.

“No food source has been confirmed yet but we placed a hold on that food so that we could do testing on it,” Clark said.

Wendy’s sent News 8 a statement on Monday saying it is taking steps to attempt to mitigate any possible contamination.

“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 discarding and replacing the sandwich lettuce at some restaurants in that region. The lettuce that we use in our salads is different, and is not affected by this action. As a company, we are committed to upholding our high standards of food safety and quality.”

Wendy’s

Health officials say in addition to contacting your doctor if you become sick, you should report E. coli cases to your county health department.