The Ministry of Social Development office in Kaikohe has been closed for an unknown duration after an arson attack described by a fire investigator as "senseless, deliberate and malicious".
The attack means clients in need of help in the Kaikohe area will have to contact MSD by phone or online.
Any that need to meet staff face-to-face may have to drive long distances at a time when petrol prices are sky-high and many families are struggling financially.
The Kaikohe Fire Brigade was called out to the government agency's service centre on Memorial Ave, not far from the Far North District Council chambers, just after 2.30am on Monday.
Two crews responded with the first arriving within seven minutes of the call, fire chief Bill Hutchinson said.