The Wainoni building, under which Tisha Cecelia Lowry, 28, and Rebecca Sarah Somerville, 35, were discovered by police, contained two semi-detached houses -- both of which were unoccupied.
A Fire Service spokesman said multiple emergency calls were received before 10pm and the local New Brighton brigade responded.
A second unit from the city station was also called, but half of the building was already well ablaze.
The spokesman told NZPA half the building remained intact after the flames were extinguished.
Mrs Somerville's husband, Jason Somerville, 33, who lived with his wife at the property in question, has been charged with murdering both women.
The family living next door moved out when they discovered bodies had been buried underneath.
