() Approximately 30 children were rushed to the hospital Friday with a mystery illness that also led to the evacuation of two school buildings.

First responders rushed to Mapleton High School in Ashland, Ohio, at approximately 10:20 a.m. local time after numerous children unexpectedly fell ill from an unidentified substance.

At Mapleton Middle School, students reported experiencing headaches, nausea, and dizziness, according to local affiliate WJW. Some students mentioned feeling shaky, and 30 children were transported to hospitals.

The schools were evacuated as first responders investigated. They ruled out a gas leak, and it’s unclear what caused the students to get sick.

“In an abundance of caution, both Mapleton Middle School and Mapleton High School were evacuated to guarantee the safety of all students and staff,” Mapleton School Superintendent Scott Smith stated in a letter addressed to students and staff.

The children were said to be doing well after being taken to the hospital as the investigation into what made them sick continues.