The blaze broke out at around 4:30 a.m. at a two-story home in the 600 block of Randolph Street, according to Allentown Fire Capt. John Christopher.
When firefighters arrived, they noticed heavy smoke and flames and went straight into the house, where they discovered a man on the first floor, Christopher said.
Crews pulled him out of the home, but he was pronounced dead at the scene by the county coroner, he added.
The man was identified as 41-year-old Otoniel Fernandez, of Allentown, according to the Lehigh County Coroner's Office.
Firefighters spent about 30 minutes extinguishing the majority of the fire, which had spread from the first-floor living room to upstairs, Christopher said.
At least three cats died in the fire, and no other residents were discovered, according to Christopher.
There were no smoke detectors found in the home, he added.
An autopsy will be performed on Wednesday to determine Fernandez's cause and manner of death, the coroner's office said.
The cause of the fire is still under investigation by the fire marshal's office.
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