Fire crews in Dunedin are warning that while heavy rain will help them extinguish the last patches of a large fire, there's a risk it may cause flooding.
The crews are currently battling small pockets of flames, but have largely contained a blaze which broke out around 5pm on Wednesday in the suburb of Burnside and forced around 100 homes to be evacuated.
Three industrial buildings and around 20 hectares of vegetation were torn through, but the evacuated homes were left unscathed. Evacuees have now been told they can return home.
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Fire incident controller Phil Marsh told The AM Show on Thursday morning that a deluge of 52ml of rain is anticipated to fall on Thursday.
"We've woken to some heavy rain this morning, which is quite good from our perspective," he said.
"We might go from one extreme to another with some possible flooding around today."
However he added that the blaze is "fairly deep-seated", and might not be fully extinguished despite the downpour.
"There'll be a lot of fire crews dealing with those hotspots. We've got some excavators on the scene at the moment that have dug a fire break on the western side," he said.
"We've had six crews overnight, and three crews patrolling urban areas to make sure things haven't spread into there."
He also says reports of explosions are nothing to be concerned about.
"There have been some drums of tar and oil and other odds and sods at some of the sites that are there, and that's what's been exploding," he said.
"We've had extreme fire conditions, which has led to the behaviour of this fire. [There have] been extremely hot temperatures, which is unusual for such a prolonged period in Dunedin.
"That, combined with the wind picking up, [meant the blaze] just took off like a rocket."
On Wednesday night, police evacuated businesses and homes in the area and closed the motorway in both directions. Parts of Dunedin's southern motorway are still shut, police say.
A welfare centre was also set up for people displaced by the fire at the St Clair Golf Club on Isadore Rd.
About 14 people had made their way to the centre, and stayed there until they were given the all-clear on Thursday morning.
Meanwhile a blaze in Invercargill is also keeping southern fire crews busy.
Firefighters stayed at a forest company yard on State Highway 1 at Awaraua overnight after it broke out yesterday afternoon.
Extra help will arrive at first light to work out how they will extinguish the controlled fire.