UPDATED 7PM: A firefighter's been injured in a blaze in Upper Hutt.

Twenty fire crews and a helicopter's been involved in fighting the fire, which broke out on the hills behind Maidstone Park about 3.30pm.

A rural firefighter has minor burns to his back, and is still on the scene of the two-hectare scrub fire.

Two fire trucks have gone up Seymour Grove as a precaution, as that's where the closest homes are.

A fire service spokeswoman said it's quite an inaccessible part of the hill, which is making the fire fight more difficult.