The fire erupted on the ground floor of the building in downtown Zhengzhou, Henan's capital.
Reports said the deaths occurred on the top floor of the building, meaning the victims likely died from carbon monoxide poisoning.
The building contains to some 30 to 40 households, witnesses said.
The fire broke out in an electricity meter box, state-run Xinhua news agency reported.
The four injured were being treated for burn injuries at an area hospital.
The fire, the cause of which remains unknown, was put out this morning.