CHELSEA, MASS. (WHDH) - At least six people were injured and 30 were left without a home after crews worked to put out a house fire in Chelsea overnight.

Officials told 7NEWS one person had to be rescued by ladder after a fire started in the back of a home on Cottage Street sometime before 12:30 a.m.

Two firefighters were among the six people injured Wednesday morning. Video sent to 7NEWS showed at least one firefighter passing by the flames on the scene’s ground level, seconds before what witnesses described as a loud explosion.

Chelsea Fire is still investigating the fire’s cause but told 7NEWS it appeared to have started on one of the home’s back porches and burned on all three of the building’s floors.

23 adults and 9 children were believed to be in the building at the time, with nearly all residents able to leave on their own, save for one person who had to be rescued via ladder.

According to Chelsea’s fire chief, the two firefighters injured during the blaze suffered exhaustion-related injuries.

This is a developing story; stay with 7NEWS on-air and online for the latest updates.

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