The Fire Service says investigators will return on Monday morning to the scene of a possible arson in central Christchurch.
On Sunday, eight appliances fought a large fire in a single-storey commercial building on Welles St, between Colombo and Manchester streets.
The Fire Service says investigators were unable to get into the building at the time because the roof was starting to collapse.
The council-owned property, which used to belong to prominent property developer Dave Henderson,
was being used mainly for storage.