Firefighters were met by heavy flames and smoke when responding to 270 Clerk St., around 10:45 a.m., Hudson County Prosecutor Esther Suarez said.
The two-alarm blaze was confined to the second floor of the home, where the woman was found unresponsive in her bedroom, Suarez said.
The victim was pronounced dead at 11:44 a.m., the prosecutor said.
One Jersey City Fire Captain was transported to the Jersey City Medical Center for treatment of minor injuries. The fire was reported under control just before 11:40 a.m.
The origin and cause of the fire remain under investigation, and the cause and manner of death are pending with the Regional Medical Examiner.
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