Dropping fire retardant from the air is one of the options being considered by firefighters now in their 13th day of battling the Kaimaumau wetland fire.
In a briefing at Wharemaru Marae yesterday morning, incident controller John Sutton told local residents the fire had now spread across 2360ha of mostly conservation land. The fire perimeter measured just under 40km.
He warned residents extinguishing the blaze would not be a quick job.
''There's a lot of work to do before it's safe to withdraw our crews and equipment,'' he said.
Options for the ''really hard mahi'' that still lay ahead included continuing to put in firebreaks, either with shovels or machinery; back-burning to remove unburnt fuel; and the use of chemical fire retardant.
An expert on the use of retardant was helping the team put a plan together and the area's iwi/DoC co-management group had given permission to use it — but only if it was really needed.
During the Boxing Day breakout, the fire crossed containment lines and advanced as far as SH1 near Srhoj Rd, Sutton said.
No homes were damaged but thick smoke forced emergency services to close the highway for two hours from 6.30pm, leading to long queues of holidaymakers.
Weather conditions had become more favourable for firefighting since then, with high humidity and benign winds.
However, that changed again yesterday with lower humidity and increased wind and sunshine, forcing firefighters to be extra vigilant.
Groundwork was focused on extending and widening containment lines.
Meanwhile, security is being put in place at key points to stop people trying to enter the fire ground at night via newly cut firebreaks.
The ground was still so swampy it was possible to get trapped waist-deep, which would be ''extremely dangerous'' if the fire made another run.
Fire contractor Kevin Ihaka said security, which would be in place from 6pm to 6am, was not there to restrict people.
''It's about keeping you safe. There's very little we can do with this fire when it does those big runs.''
A team from Fire and Emergency New Zealand (Fenz) Urban Search and Rescue has also been sending up a drone with thermal imaging gear to look for hotspots by night.
One was found on Tuesday night in the burnt area near Kaimaumau village so a ground crew went in on Wednesday to investigate.
The drone crew worked at night because hotspots showed up better and so they didn't have to share airspace with helicopters.
Far North Mayor John Carter also addressed yesterday's briefing, praising the response of the local community and the efforts of firefighters and other services involved.