At least four students were sickened with salmonella earlier this week, at a school in Hamburg. One of the students ended-up at a hospital in Omaha, but was later allowed to go home. KETV in Omaha reports parents of students at the Marnie Simons Elementary received a letter Tuesday alerting them to the medical issue. The first salmonella case appeared Oct. 1st, with additional cases being reported on Oct. 7.

So far, no one knows where the salmonella came from. Most parents said they knew about the sick children before the district sent its letter Tuesday. The news came from their kids.

Superintendent Jay Lutt said the district’s food supplier hasn’t found any evidence of salmonella or any cases related to its food products. Because the source remains a mystery, parents want faculty to be extra careful, while at home, those same parents are making sure their kids focus on personal hygiene, especially thorough hand-washing.