Authorities urged local residents to remain at home with doors and windows shut and to avoid going near the affected area.
The incident has affected 17 people; ten were taken to hospital, including five children. According to the Emergency Medical Service (SEM), the others were treated at the scene and discharged, as they only suffered minor injuries.
Emergency services received the alert at 14:12. Firefighters immediately evacuated the facility, set up a safety perimeter and deployed several crews to bring the situation under control, while specialist teams began neutralising the chemical mixture and emptying the tanks involved.
Although the toxic cloud has been dissipating, the council is maintaining the recommendation of confinement as a precaution until intervention teams complete the decontamination work.
For the moment, it is not yet known which substances triggered the chemical reaction.