Firefighters have contained a large bush fire that came dangerously close to destroying the main power feed between the North and South Islands.

A house and several out buildings were destroyed in the blaze at Port Underwood, 20km east of Picton, but fire crews managed to save a further five houses that were threatened by the 6-hectare blaze.

Two firefighters also suffered minor injuries, one from the Koromiko Rural Fire Force who was overcome by smoke and a Fire Service member who bruised his ribs and a kidney when he slipped and fell.

The fire started at 3pm yesterday when a tree came down across powerlines.

"There was no call of fire in the initial stages but we dispatched two helicopters anyway, given the remoteness of the site and the high probability that any downed power line in 35-knot winds would cause a fire,'' said Marlborough Kaikoura Rural Fire Authority principal rural fire officer Richard McNamara.

"Unfortunately, when the first aircraft got there the first house had already been affected by fire with smoke coming out from under the eves so we stood no chance of saving that one but by getting aircraft in there quickly, fire crews managed to save five other houses that were under threat.''

Up to 10 residents were forced to evacuate from the area while fire crews battled the out-of-control blaze.

The isolated location combined with strong winds and steep terrain meant the operation was very difficult.

The fire came dangerously close to the high voltage direct current (HVDC) inter-island link, which connects the North and South Island's electricity networks.

"That would have been very ugly,'' Mr McNamara said.

This morning the fire was fully contained but crews remained at the scene dampening down hot spots.

"We've worked very hard to save those houses and we don't want to lose them now.''

Residents had last night been told they could go back to their homes.

Mr McNamara praised the efforts of the fire crews and aircraft operators involved in the operation.

"Without them, we would have lost at least five houses and the main DC link would have been under threat. It was a fantastic effort in a very remote area. Everyone did their best for the residents out there.''

additional reporting by The Herald on Sunday