The Fire Service has confirmed a blaze at a Work & Income office in Auckland on Sunday morning was deliberately lit.
Firefighters were called to the office in Panmure about 3.50am on Sunday and arrived to find the building fully alight.
Five fire engines were used to bring it the blaze under control.
Investigator Russell Dickson Dickson said there was extensive smoke and heat damage to the entrance and the ceiling cavity, but the building does not appear to have any serious structural damage.
Police are speaking to a local man about the fire.
Work & Income said it will make alternative arrangements for clients who usually use the offices. Those with appointments on Monday will be told to go to other branches nearby.
Work & Income said about 23 people are employed at Panmure and they will work from other offices.