The Fire Service says an investigation into a large blaze that gutted a Christchurch building and injured three firefighters could take several days to complete.
The fire broke just after midnight on Wednesday in a large commercial complex on Birmingham Drive, Middleton, near Addington Raceway.
The firefighters fell three to four metres when a floor on the second storey of the Trimble Navigation building gave way as they were investigating whether the blaze was spreading.
Two people have been discharged from hospital on Wednesday, while the third has had surgery on his knee.
The Fire Service's assistant national commander, Dan Coward, says two investigations have begun.
One is looking into the origin of the fire, which should be completed by Thursday, he says. The second will take a few more days and focus on why the firefighters fell.
Mr Coward says investigators will look at what caused the floor to collapse and whether the earthquakes in September last year and February played a part.
"At this stage there are some indications there has been (earthquake) damage and that was based on visual signs of areas being cordoned off by tape, but that could also suggest other things for the building," he told Morning Report.
Mr Coward says an investigation will look at whether there was already a hole in the floor due to another stairwell having burnt through while the fire was being tackled.
Senior Station Officer Mike Balmer says there is no formal register crews can use to tell if a building is an earthquake risk. They have to have a good look at the structure and determine in each case whether it is safe to enter.
At the height of the blaze, 40 firefighters and 10 fire engines were used, including two engines with ladders and hydraulic platforms. Firefighters were able to contain the fire to half of the complex.
Building not unsafe - owner
Trimble Navigation's Christchurch managing director Corrine Haines says the building suffered only minor damage in recent quakes in Canterbury and was not unsafe.
Ms Haines says structural engineers have told the company the second story was safe to use, and for workers to carry out repairs. The company opted to put all staff on the ground floor.
A Trimble Navigation worker told Radio New Zealand's reporter at the scene that staff were using only the ground floor, and that workmen were carrying repairs were on the second level to services such as air conditioning.
Ms Haines says staff are already dealing with difficult situations and making do with reduced space.
She is very conscious that for some people, the fire may be the last straw, but hopes that some staff will return to work next week.
However, she says she cannot guarantee there won't be any job losses among the 240 staff at the site, but Trimble Navigation's parent company in the United States is committed to rebuilding in Christchurch.
