Firefighters tell Action News it quickly went to a second alarm as the flames spread to six units.
One person was trapped on the second floor of one of the homes, but was rescued from the fire.
The 12 animals that were killed included dogs and cats from different homes.
Initial reports indicated an explosion may have touched off the fire.
However, after Peco crews spoke to the fire chief and the fire marshal, they've determined there was no gas expolosion that caused the fire.
No injuries have been reported.
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