Chelsea firefighters used a ground ladder to rescue a child from a burning building just after midnight Wednesday.
The bulk of the fire was in the rear of the triple-decker, firefighters told WCVB, adding that porches collapsed as the flames intensified.
Thirty residents managed to escape the fire. Four civilians and two firefighters were transported to the hospital for treatment. The crew suffered exhaustion.
"It was a very, very labor intensive fire -- five alarms worth of companies, all our mutual aid partners. Our first arriving companies did a tremendous job -- a tremendous job. Very strong work to contain this to the building of origin," Chelsea Fire Department Chief Leonard Albanese told reporters.
The cause of the fire is under investigation.
