The roughly 20 fifth graders at a north Alabama elementary school who became ill after eating lunch last month did not eat raw chicken, according to the state Health Department investigation into the incident.

The probe also did not determine a cause.

One of the students was taken to a hospital while others complained of nausea following the incident at Sugar Creek Elementary School in Limestone County.

While some of the affected students’ parents alleged they were fed raw chicken tenders for lunch, Limestone County Schools Superintendent Randy Shearouse disputed the claim.

On Friday, the Alabama Department of Public Health investigation into the incident backed up Shearouse. But the agency’s probe could also not identify a virus or bacteria that could have been responsible for the students’ sickness.

“The Alabama Department of Public Health (ADPH) determined that the children did not consume raw poultry products at the school, as the products were precooked,” the agency said in a statement. “Stool specimens, collected as part of the investigation, did not result any pathogens that could be linked to an outbreak. No children were hospitalized, and all have recovered.”