A chemical spill in a science class caused Donna High School to evacuate students.
Officials said 26 people were transported to Knapp Medical hospital for observation, including a teacher and a security guard.
According to the Donna superintendent, a teacher knocked over a jar that held a dead specimen with formaldehyde.
Formaldehyde is a colorless, flammable, strong-smelled chemical that TMs used to produce many household items, according to the United States Environmental Protection Agency (EPA).
When exposed to the chemical, it can cause watery eyes, burning sensations in eyes and throat, nausea and difficulty breathing.
According to EPA, it is known to cause cancer.
No students were in the classroom at the time.
First responders were called to the campus around 10 a.m. Friday morning.
Witnesses said some students did inhale the chemicals.
Authorities told Action 4 News that the school has old chemicals stored in a science lab.
According to Donna High School administrators, students and staff evacuated the building after a fire drill was set off.
Maintenance and a fire emergency team were at the scene.
The high school released students for the rest of the day.
Administrators at Donna High School told Action 4 News that text messages were sent to parents from the school.
According to administrators, parents received text messages about only a fire drill.