City firefighters responded to the fire at 120 W. Maple St. at 10:26 p.m. Thursday, said Luzerne County 911 officials.
John J. Seliga, 52, died in the blaze, according to Luzerne County Coroner George Hudock. An autopsy performed Friday afternoon revealed Seliga died at 11:45 p.m. Thursday of burns and smoke inhalation while trying to escape from the building.
The names of the four who were injured were not released Friday night.
State police, District Attorney Dave Lupus and the Hazleton Fire Department continued their investigation well into Friday night.
Crane said it was too early to determine if the fire was an arson. "There's a lot of unanswered questions."
The boarding house had a revolving door of residents, according to Hazleton Mayor Louis Barletta, who went to the scene after Thursday's city council meeting.
There were 19 to 25 residents in the three-story house when the fire started, he said.
"By the time I got there, the flames were above the library building, which was two buildings away," Barletta said. "It was apparent that if there was anyone in there, they would have difficulty getting out."
