Fire crews arrived at the home on Palisade Avenue just after 12:30 a.m.
Firefighters found gas canisters at the scene of the fire and signs on the front door of the building showed that smoke and carbon monoxide detectors were not working.
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Officials say multiple residents were trapped in the basement when first responders arrived.
A broken basement window allowed air into an apartment where rescuers bravely saved a couple trapped inside.
Two residents were badly burned in the fire and another is being treated for an unknown injury, authorities said. They were taken to Hackensack University Medical Center.
A handful of firefighters who ran into the basement are also being checked out for minor injuries.
There is no word on how many people were impacted by the blaze.
Crime scene investigators are using a canine to help gather clues about what caused the fire.
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The Bergen County Prosecutors Office will investigate the cause of the fire.
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