It happened on the 200 block of South 8th Street at around 1:30 p.m.
Residents in the area reported hearing a loud explosion which came from underground, causing the transformer fire.
PECO and Hazmat responded to the incident. They were able to gain quick control over the situation.
The evacuated residents, reported as 7 adults and 7 children, were taken to 850 Locust Street until they were let back in.
