Police and fire crews responded to the 1100 block of Woodland Avenue in Sharon Hill, Delaware County for a possible explosion and fire just after 2:30 p.m.
Officials say everyone is out of the building. One person was taken to the hospital for smoke inhalation.
Neighbors said they heard a loud “BOOM” before the flames erupted.
The fire went to 3-alarms with crews from more than 15 companies called to respond.
Residents in all six apartments were displaced. The American Red Cross was providing assistance to residents from at least five of the apartments.
Hundreds of fire and police have been working on getting this fire under control. Crews from Sharon Hill, Folcroft, Brookhaven, Holmes, Upper Darby and others are on the scene.