The Red Cross assisted about a dozen people after a triple-decker fire in Woonsocket Friday night. According to fire officials, it started at about 7:30 p.m. behind 158 South Main Street. The fire was mostly contained to a wooden deck and stairs at the rear of the building but did extend into the interior as well. It took firefighters about an hour to extinguish the flames, although units were on the scene for about three hours in total. There were no injuries reported. Fire officials put the number of residents who were displaced at about a dozen, possibly as high as 17. The cause of the fire is still under investigation.