Nineteen households along Waitangi Wharf - Owhenga Road in the Chatham Islands have been evacuated, ahead of a fast-spreading fire.

Photo: Supplied / New Zealand Defence Force

The fire was burning towards the southern coast, but emergency services were expecting a wind change overnight.

The fire - south of Waitangi Wharf - started early on Thursday, and has now burnt through about 2000 hectares.

Chatham Islands mayor Alfred Preece said the evacuations were a precautionary measure and he was confident fire-fighters had it under control.

"We really are at the mercy of Mother Nature and, yeah, we don't want to see any conservation reserves get severely impacted by this fire, but the safety of people is number one."

Mr Preece said conditions had been very dry but it had just started to rain softly, which hopefully would help firefighting efforts.

A Defence Force plane has sent back images of the fire to help officials organise how to battle the blaze.

Principal rural fire officer Craig Cottrill said the fire was in a very remote location, making it difficult to access.

Access issues and the dry windy conditions had put the focus on precautionary work to protect structures, and cutting firebreaks in case of a wind shift, Mr Cottrill said.

Eight Fire and Emergency volunteers and four Department of Conservation staff had been fighting the fire along with three local contractors.

Mr Cottrill said they were now moving to actively fight the blaze, and more firefighters and supplies would be sent to the Chathams.

"A helicopter with long-range tanks will arrive on the island tomorrow (Saturday), as will an incident management team that will ensure the right resources are being mobilised."

Photo: Supplied / New Zealand Defence Force

The Defence Force sent a C-130 Hercules aircraft on Friday to conduct an aerial survey to help Fire and Emergency determine the scale and spread of the blaze.

A chartered Air Chathams plane will fly more firefighters and fuel to the island on Saturday morning.

Chatham Islands is an archipelago in the Pacific about 800km east of the South Island.

About 600 people live on two of the 10 islands that make up the Chathams and rely on conservation, tourism, farming and fishing.