It happened Monday before 2 a.m. in a two-story house that has been converted into separate apartments on the 300th quarter of Private Street in Potstown.
Officials say a fire alarm has sounded, warning residents of the danger.
Three people lived in one apartment, two in the other.
Firefighters told Action News that one resident jumped out of the building to escape the flames.
The man was taken to Reading Hospital for treatment.
The fire with 2 signals spread to the second house before firefighters took control.
A firefighter injured his knee while fighting the fire.
The Red Cross provided assistance to the displaced.
The cause of the fire is being investigated.
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