The incident, which occurred at around 7.30pm on Sunday evening, is believed to have been caused by a gas leak which resulted in two strong blasts.
On Sunday night, firefighters were at the scene to tackle a blaze that raged inside the building, caused by the explosion.
Lisbon Councillor for Civil Protection Carlos Castro confirmed injuries were caused by the blast in the four-storey building, and that all the victims were inside the building at the time, some of whom were foreigners.
Several people were left homeless.