Firefighters have contained a "suspicious" bush fire in Northland that at its peak threatened 30 homes.

Emergency services were called to the blaze on North Rd in Kawakawa about 5pm, Fire Service northern communications shift manager Jaron Phillips said.

Crews faced extremely difficult conditions tackling the 3000sq m blaze, including access to the fire.

Initial reports suggested it was only 300sq m.

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"Access is near impossible, that's what I'm told by fire crews on scene. They're dealing with 20-30 knot westerly winds and they're just setting up to protect those homes," Phillips said.

A helicopter with a monsoon bucket had been deployed to assist crews on the ground.

The Fire Service said the blaze was suspicious and a fire investigator was set to investigate what started the fire.