Sarnia Fire Rescue responded to a fire in a building attached to Sarnia Jail on Christina St. N at around 6:15pm Monday evening.
Fire officials say two barrels of chemicals used in the water boiler caught fire.
Firefighters had to don hazmat gear to extinguish the flames and were on scene until around 5am Tuesday when an outside hazmat contractor arrived to clean up the scene.
The cause of the blaze is not known. There was no smoke or hazard inside the actual jail building that houses prisoners.
