The fire was being whipped along on several coal ridges by high winds.
SEC officials hoped the fire could be contained by early this morning.
But intense heat, mud, dust and acrid smoke made the battle almost impossible for firemen.
The fire is the biggest coal blaze in the Latrobe Valley for 33 years.
It was first noticed about 1 p.m. By late afternoon clouds of smoke and dust covered most of the town of Morwell.
The SEC still isn’t sure what started the blaze.
A wind change and heavy rain about 6:30 p.m. turned the fight in favour of the firefighters. The coal dust, with a 66 per cent moisture content, became soggier.
But sulphur-dioxide fumes continued to be a problem.
Mr. George Bates, the SEC’s area manager, said coal production would slow down, but Victoria’s electricity supplies would not be affected.
But the Morwell, Hazelwood and Yallourn power stations were generating only 900 megawatts compared with 1618 before the fire.
Supplies of the briquette coal had stopped. All three conveyor belts from the open cut were out of operation last night.
The fire started in the north-western edge of the 306-hectare, 140-metre deep open cut.
Eighty kilometre-an-hour westerly winds quickly fanned the fire and it spread across the seven main ridges to engulf about one-third of the open cut while 250 men were at work.
SEC coal experts believe the fire burnt to a depth of only about 14.4 centimetres of the residue coal dust around the face.
“It is highly unlikely that brown coal would burn deep underground,” the expert said.
The open cut has coal to a depth of about 100 metres, with a 10-metre overburden.
The veins run under the town of Morwell, but Mr. Bates said there was no danger to the town.
The closest homes are about a kilometre from the open cut.
RAAF Men Brave Heat of Morwell Battle
The day was marked with thick acrid smoke.
Last night there was a volcanic extravaganza of sizzling, fizzing sparks across the northern face of Morwell’s giant open cut mine.
At 11:30 pm, about 400 firefighters had clambered up and slipped down the wet coal-mud slopes, pouring thousands of gallons of water and foam into the numerous spot fires.
They were men of iron lungs.
Thick smoke, mixed with sulphur-dioxide fumes, covered the area.
Around them were some areas too hot to even approach. Seven centimetre steel conveyor cables burnt through. Hard rubber melted like plasticine.
Surveying the scene the man in charge of the firefighting operation, Mr. Jack Vines – the SEC’s coal production manager – said it was like a “huge burning briquette.”
“Brown coal takes a long time to burn but once it does it’s very hard to put out,” he said.
One of the firefighters, Corporal John Scott, of East Sale RAAF Base, said: “It was shocking… the heat, the wind, the smoke and the coaldust.
“The worst bit was the hot dust in the eyes.
“You’d put one fire out only to see another start up somewhere else,” Cpl. Scott said.
His commanding officer, Squadron Leader Larry Crowley, said most of his 72 men were not firefighters.
“They’re volunteers. They were doing their normal jobs at the base from 7 am before volunteering at 4 pm,” he said.
Another 80 RAAF men will relieve the men today.
Two of the firefighters, LAC Mick Preece and LAC Sid Overy, collapsed and had to be given oxygen.
The ever-present St. John Ambulance Brigade were on hand dispensing first aid, coffee and good cheer.
Mr. Vines said later coal deliveries had resumed to the Hazelwood power station and one of three dredges put out of action earlier had its power restored.
“There appears to be no permanent damage – we have been able to do maintenance work and keep up supplies while firefighting,” Mr. Vines said.
He said this morning would be crucial.
“It will depend on the wind direction… we expect to be keeping close surveillance at least over the weekend.”