Northland farmer Susan Bradley moved stock and her family were ready to evacuate as a fierce forest fire encroached on her home near Kelly's Bay yesterday.

It was one of two farm houses being monitored in case the fire spread or changed direction.

Mrs Bradley said her 16-year-old daughter had packed some bags ready to leave, while she and her husband had moved 400 lambs and 70 cattle away from paddocks near the blaze. They had also moved neighbours' stock.

She spotted smoke about 8.30am in the direction of Kelly's Bay, 50km southeast of Dargaville. The fire started in swamp and scrub land in a Department of Conservation area called Punahaere Creek but then jumped a road into a forestry block.

Strong winds had fanned the fire closer to their Poutu Topu Trust farm where her husband had been the manager for seven years.

As Mrs Bradley spoke to the Northern Advocate, she could see flames while looking out her kitchen window and admitted the situation was a "little scary".

Deputy principal rural fire officer for Kaipara Kevin Ihaka yesterday called the fire suspicious. A fire investigator was at the scene.

By 4pm the 40-hectare fire was about 80 per cent contained, with three helicopters helping douse the blaze, aiding fire crews on the ground. Two other helicopters were on standby. Two bulldozers and two diggers were creating firebreaks and it was hoped the fire would be fully contained by nightfall, though concerns remained that it would jump Pouto Rd and get into hundreds of hectares of pine forest.

Mr Ihaka said a small fire at the Kai Iwi Lakes yesterday was also suspicious, adding to his concerns that these fires were being deliberately started.

"It's a small rural area and we'd be keen to hear from anyone who saw vehicles coming and going in the area. Areas like this not only put residents and property at risk, but firefighters and stock ... they cost the ratepayers and taxpayers a huge amount of money ... whoever is doing this has a problem."

Department of Conservation area manager Kauri Coast Meirene Hardy-Birch said a staff member heading to the area about 9.30am had seen smoke and alerted the office.

A department team of about 12 firefighters plus a team of rural firefighters and forestry contractors were at the blaze and were expected to remain on site overnight. The helicopters were expected to be back in the air today.

Helicopters were using monsoon buckets to collect water from dams in the forest and from the sea to dump on the blaze.

"The challenge is the unpredictability of the weather, and being so close to the sea adds another dimension," said Ms Hardy- Birch.

The fire was expected to be monitored for at least the next few days.

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