The emergency services and Scottish Gas were called to the property in Highholm Street in Port Glasgow, Inverclyde, at about 2.25pm.
A man and a woman were taken to Inverclyde Royal Hospital for treatment following the incident.
A Police Scotland spokesman said: "The extent of their injuries is not known but they are believed to be non-life threatening."
Several houses in the area were evacuated as the building was thought to be unsafe.
Those affected have not yet been allowed to return to their homes and arrangements are being made for alternative accommodation, police said.