Firefighters brought under control a five-alarm blaze that displaced 17 adults and three children from three apartment buildings Saturday, according to fire officials. A firefighter and a resident were treated for minor injuries, said Northbridge firefighter Gary Noel. The apartment buildings, each three stories, were engulfed by the fire, which started at 75 Church St. and spread to 35 Cross Place in the Rockdale neighborhood. The first two buildings were destroyed, Powers said. The Fire Department first received a call about the fire at 1:52 p.m, Noel said. The fire spread quickly, causing the first building’s roof to collapse, and spread to the other two buildings, he said. It was brought under control at 5:41 p.m. Red Cross of Eastern Massachusetts set up a service center at St. Peter’s Church to determine the needs of residents.