Concerned locals are offering a $5600 reward for information after a spate of deliberately-lit fires near a West Coast kiwi sanctuary last weekend.

The first of five fires was discovered in Westland National Park near the Okarito Kiwi Sanctuary, about 25km north of Franz Josef, on February 7. The sanctuary is home to the rarest kiwi species, the rowi, of which only 350 remain.

No kiwi were harmed, but the taxpayer cost of fighting the fires was estimated to be up to $50,000.

Locals last week blamed hunters, who they said had been lighting fires in the area for decades in order to attract deer with regenerating grass shoots.

Richard Saunders, who operates Okarito Nature Tours, said local businesses and individuals had stumped up the reward money to send a clear message that deliberate fires would not be tolerated.

"Enough is enough. Too many people realise it's costing everybody through their taxes, it's endangering kiwi, and it's desecrating a national park, so it's got to stop," he told NZPA.

"It's important for the community to stand behind the Department of Conservation in this and support them, because it's a community problem."

Mr Saunders had been "overwhelmed" by those who had contributed to the reward.

"A firefighter fought the fire for free all night long, lost business the next day, and paid for it through his taxes as well, and then was still able to stump up a significant amount. I think that's really telling."

The reward would go to anyone who had information leading to a conviction, although Mr Saunders hoped the reward would not be necessary.

"I think common decency might prevail."

Constable Bill Parker of Franz Josef police said the reward might lead to information which had not come forward so far.

"We haven't really got much to go on, but we're still looking at a couple of suspect vehicle descriptions," he said.

"People have heard others saying various things, so we're just following down those lines of inquiry to either eliminate them or establish what's actually been said."

Nobody had been charged over any of the previous fires, Mr Parker said.

"There have been suspects, and obviously those suspects are being looked at again."

Police had not yet been determined if the fires had been lit by hunters, he said.

"We're just slowly working through the rumours and any information that we get and going from there."