WATCH: One missing after general alarm blaze tears through LaSalle townhouses

A major fire tore through three townhouses in LaSalle late Tuesday.

Firefighters were called to the condo block on Bois-des-Caryers St near Rosaire Gendron St at about 10:30 P.M.

Despite taking only six minutes to arrive at the scene, the flames spread quickly, with a general alarm being called not long after.

About 200 firefighters and 75 vehicles were brought in to help control the blaze, which caused the roof to collapse and more extensive damage. All three homes were destroyed while a fourth, located behind fire, sustained about $50,000 in damages.

Multiple residents were treated for shock; a 61-year-old woman is unaccounted for. 

The exact cause of the fire is in under investigation, but is believed to be arson. Witnesses told investigators they saw three individuals running from the rear of the building shortly before the flames broke out.