An investigator looking into the blaze that engulfed an Auckland apartment block has confirmed the fire was deliberately lit.
Four residents had to be rescued from the two-storey block in Commerce Street as about 80 firefighters battled the flames on Sunday morning.
Senior fire investigator Michael McEnaneysays an apartment was unlocked and someone set light to a substance in it, but no accelerant seems to have been used.
Investigators are also trying to find out who switched off the fire alarm and why.
The Fire Service says increasingly firefighters are finding buildings where alarms have been switched off rather than repaired or replaced.
Property Investors Association president Andrew King says it is now against the law for tenants to tamper with fire alarms, which is a positive change, but difficult for property owners to enforce.
Auckland councillor George Wood, who chairs the council's community safety forum, says it's vital buildings are properly equipped with fire alarms, and he'll be following that up with staff this week.