Three people were hospitalized Thursday evening after a chemical spill at a Mentor Biologics lab on Science Drive released highly toxic and flammable chlorine dioxide into the air, Madison Fire Department spokesperson Bernadette Galvez said.

“The call first came in as a spill but…there were three patients, they inhaled the chemical, so it wasn’t on their skin but they inhaled it,” Galvez said. “Everybody was talking and they were all alert but they were, all three, were taken to the UW hospital.”

Galvez said the fire department is still unsure how the chemical leaked in the first place, but speculated it could have been a result of research in the lab.

Galvez added that all the patients were alert and speaking when paramedics transported them to the hospital.

A statement form the fire department said Madison hazardous materials teams stayed at the scene to ensure the building was safe for employees to return.