Extra fire crews have been brought in today to try to contain a large blaze on conservation wetlands at Awarua, south of Invercargill.
The fire, which started on Saturday and extends from the head of Awarua Bay to the Waituna Wetlands, has burnt through about 1000 hectares containing peat.
Fire and Emergency said it is almost guaranteed to get bigger today, with a change in wind direction forecast for this afternoon.
Fenz said the fire ground was difficult to access on foot and crews were likely to be working for a fortnight or more to fully extinguish the fire.
It was tough work, Mawhinney said.
"It's a bit ironic, you can fall into holes full of water while you're trying to put out a fire, but equally there is the danger of falling into an ash pit, which could be 500 degrees Celcius ... these guys are doing it hard out there.
"Peat fires mean we'll be out here for weeks - hopefully weeks, not months - but they are deep-seated fires, ash pits very hard to put out. That will be a real frustration, complicated by the drought that we're having here in Southland."
The area is an internationally significant wetland.
There are a number of fishing huts and maimai for duck hunters in the area and although they are in the direct line of the fire, none are at risk at the moment.
Mawhinney said the forecast was for a change in wind direction so the fire could be going in an entirely different direction. He asked people to stay away from the area.
Bluff Community Board chairman Raymond Fife said drought conditions had left the area quite dry.
"We haven't had any rain of any description for months and it was a worry something like this could happen, even this time of year."
Fife said he was concerned about how long it would take to put the fire out, given it was burning in peat.
Dean Whaanga, kaiwhakahaere for Awarua Rūnaka, said Awarua-Waituna was significant to Ngāi Tahu whānau and to the local community.
"We are thankful for the quick response from Fire and Emergency as they go about protecting this special place and the taonga species that live there."
Awarua-Waituna is one of New Zealand's largest remaining coastal wetland systems, one of five significant wetlands in DoC's national Awarai Kākāriki wetlands restoration programme. It is home to many wading birds and other species.