The four firefighters were inside a discount furniture store located on the 2400 block of Kensington Avenue, which had caught fire as the result of embers coming from the burning warehouse, located adjacent to the store.
Two firefighters perished inside - two others were rescued from the store and taken to Temple University Hospital with what are not believed to be life threatening injuries.
Flames broke out just before 3:15 a.m. inside the abandoned Thomas Buck Hosiery Factory, located near the intersection of Jasper and York Streets.
Firefighters arrived on the scene to find heavy fire showing from all six floors of the warehouse with explosions coming from inside the building.
Embers from the blaze landed on several nearby homes and businesses, sparking small fires. A total of six homes were damaged.
Fire officials evacuated residents in the surrounding area and PECO cut power to parts of the area around the warehouse as a precaution.
The fire was placed under control at around 5:30 a.m.
Authorities are closely watching part of the remaining warehouse structure, which may be in danger of collapse.
The Red Cross is on the scene assisiting displaced residents.
Documents show the Thomas Buck Hosiery Factory operated in East Kensington until the mid 1970s, when another fire damaged the building.
This story comes from our sister station, WPVI-TV, in Philadelphia.