(CNN) -- Nearly 500 people -- including students with serious breathing problems -- were evacuated from a Denver, Colorado, hospital and an affiliated school to escape the fumes from a hydrochloric acid spill, according to fire and school officials.
Emergency workers help a patient affected by fumes from a chemical spill in Denver, Colorado, on Monday.
Of those evacuated, at least 35 adults and children were taken to other hospitals to be treated for respiratory irritation, said Lt. Phil Champagne of the Denver Fire Department.
The spill happened at an indoor pool of the Kunsberg School, a learning facility for children with breathing problems who cannot attend a regular school, according to school spokesman William Allstetter.
The Kunsberg School, which teaches kindergarten through eighth grade, is affiliated with the adjacent National Jewish Health, a medical facility that specializes in treating patients with breathing disorders.
A pool worker reported two 15-gallon drums of hydrochloric acid spilled into the pool during routine maintenance early Monday, according to Champagne. The acid came into contact with bleach, and the interaction created hazardous fumes that spread throughout the campus through a series of interconnected tunnels.
None of the 35 injuries are considered life-threatening. The workers closest to the spill reportedly suffered the worst irritation, according to the fire department spokesman.
The Kunsberg School is in a building separate from the hospital, but the two facilities are connected through the tunnels, Allstetter said. He said an estimated 400 staff members and 92 children were evacuated as a precaution. Students were taken to the Denver Fire Department headquarters where their parents could pick them up, Champagne said.
Classes are expected to resume on Tuesday, according to Allstetter.
Fire officials believe the ventilation system and underground tunnels connecting the campus buildings contributed to the fast spread of the irritant.