The call came in around 4:30 p.m. for flames showing on the 700 block of Cedar Street.
Chopper 6 was overhead as firefighters worked to get the blaze under control.
Kyle Davis lives nearby and says he jumped into action to rescue people and pets before fire crews arrived.
"If that was my family I would want somebody else helping. Once the officer said, 'just help get everybody out,' I said, 'boom let's get everybody safe,'" Davis recalled.
Crews battle multi-alarm fire in Allentown, Pa.
How the fire started is still under investigation, but officials confirm there is a police investigation as well.
"Police units responded to an incident at the scene and the situation escalated from there," said Mayor Matt Tuerk.
Right now, it's unclear why police were called and what transpired before the fire broke out.
Action News has learned that three firefighters and two residents were injured. There was no immediate word on their conditions.
Officials said about 20 people are displaced.