NEW CARROLLTON, Md. (AP) — Authorities say a two-alarm fire that displaced 120 residents from a New Carrollton apartment building has been ruled accidental.

Prince George’s County fire officials said Wednesday that a malfunctioning heating and air conditioning unit was to blame for the blaze in the 5000-block of 85th Avenue on Tuesday night.

Officials say firefighters used a ladder to rescue several people from the upper floors of the building, including an infant.

Four residents suffered minor injuries, and another 10 were treated at the scene. Officials say a firefighter also was treated at a hospital for an injury sustained while doing overhaul work.

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