Norristown FD units were dispatched to a dwelling at 311 Moore Street between Arch and Walnut at 0214 hrs. Residents advised Montgomery Co. Communications that "it may have been a bomb". Engine 27-21 arrived with a wood frame twin dwelling, heavy fire on the first and second floor. All units went in service. Occupant status is unknown at this time. Two additional engines and one additional ladder were called in from Bridgeport Borough and East Norriton Township.