Geddes said strong winds had blown the fire across the Southern Motorway, sparking spot fires in the nearby suburbs of Concord and Green Island.
''We've had hedges go up, trees go up, but aerial crews and ground crews got on to those extremely quickly.''
Residents from about 100 properties near the fire were unable to return home last night.
The huge blaze was brought under control around 9 o'clock last night, with no damage to homes.
However, Fire and Emergency's Riwai Grace says it will take days before it's fully extinguished.
The huge blaze spread to between 20 and 25ha of vegetation and forced the evacuation of about 100 homes.
It started as a small vegetation fire in Burnside about 4.45pm yesterday but dry, windy conditions saw it spread quickly with fears it might even jump the motorway.
Three industrial buildings and a shed at a residential property were damaged by the blaze, he said.
It was too early to say what might have caused the blaze, but a fire investigator had been called, he said.
Peter Chalmers, who owns the Valley Lumber yard on McLeod's Road said it was "frightening" how quick the fire developed.
Chalmers said he had lost his livelihood for the winter when up to 1000 tonne of dry wood went up in flames at an "unbelievable" pace.
It only took 15 minutes from a puff of smoke to spread to two fires in his "tinder dry" yard.
"The speed of it was just frightening."
"We were running around with fire extinguishers and buckets of water but it overwhelmed us. Little flames turned to 10 metres high," he said.
The blaze would have "a big impact on the business", he told Newstalk ZB
He said he had taken knocks in the past and would assess the damage when he was allowed back on the property.
He believed the machines on site and the businesses buildings were still intact.
The one thing he was desperate for, as were others in Otago and Southland, was rain.
Rain was desperately needed or else there would be more fires just like this.
"The weather has been great and warm but these are the repercussions."
Geddes said six fire crews would be stationed at strategic locations overnight to fight hot spots and flare-ups.
Dozens of residents were evacuated from neighbouring suburbs as smoke enveloped homes and embers threatened to spread the fire further.
Multiple fire crews, helicopters and tankers remain are at the scene where the fire broke out, on McLeods Rd.
Geddes said fire crews had been "working their butts off'.
Firefighters were "up against it'' because of spot fires, and the way the fire was travelling.
"We believe we have it contained to a forestry block, a wood pile and buildings adjacent to the motorway," he said.
There were multiple spot fires beside the motorway.
Geddes said helicopter crews were doing "a fantastic job'' dealing with spot fires, and controlling the main fire.
"The main issue now is the wind, which is against us.''
There had been explosions from LPG containers, refrigerated containers and vehicles as the fire swept through the area.
"It's extremely hazardous, extremely dangerous fire conditions, with all the risks associated with that.''
About six fire appliances were protecting properties on the railway side of Green Island.
On the other side multiple properties had been evacuated because of spot fires.
The Southern Motorway had also been closed because of the fire.
A witness from a Dunedin home situated above the blaze said the three building had been gutted by the fire. It looked as though there was significant damage to nearby houses, she said.
"One person's back yard when we were up there was on fire."
"Probably more now though since we have been home, as it has spread probably another 100m."
There were no reported injuries.
Police were helping evacuate surrounding homes and businesses as well as the lower half of the suburb of Concord due to wind and fire embers.
A welfare centre had been set up at the St Clair Golf Club on Isadore Rd, for those displaced by the fire.
Civil Defence and Red Cross Personnel would be at the centre to help those residents who need it.
Fire and Emergency New Zealand spokesman Mike Grant was advising people to stay away from the area.
"With roads closed it will cause congestion for our firefighters and crews who are working as hard as they can to stop the fire spreading," he said.
"There's embers that have carried in the wind, and they have been landing on nearby properties. We have a lot of firefighters reacting very quickly to this, and they're working through these areas to put them out."
Dunedin resident Emma Scott was one of several locals opening their doors to those without a bed for the night.
Scott said the whole lower Dunedin had plumes of smoke billowing from the streets.
"When I was picking people up from Concord I could hardly see my way home driving because of the smoke," she said.
Two people had taken her up on her offer and were sheltering at her home since leaving their own.
Meanwhile, fire crews were working to contain two more scrub and grass blazes in the area.
A scrub fire in nearby Tahakopa Valley had now been extinguished.
Four tankers and three crews remained at another blaze on Round Hill Road, inland from Karitane,
- Additional reporting by Alice Peacock
