RCMP say there were no injuries when an explosion on Saturday started the fire at a TransGas facility near Prud'homme, a small community northeast of Saskatoon.
TransGas is a subsidiary of Crown-owned SaskEnergy, and company spokesman Dave Burdeniuk said four homes in the area remain evacuated and the residents are staying with relatives or in hotels.
Burdeniuk said workers ventured into the flames twice during the night as well as on Sunday, and that equipment is being brought in so that an attempt can be made to turn off the gas at the wellhead.
"A portion of the steel building that was on top of the wellhead has melted. That will have to be removed by crane," Burdeniuk explained Sunday.
"It's a hot fire."
Flames are reaching about 20 metres into the air and SaskEnergy has asked for a no-fly zone around the site as a precaution.
Lorie Newnham, owner of the Prud'homme Hotel, said some customers told her they could see the glow in the Prairie sky from as far as the eastern edge of Saskatoon on Saturday night, which is more than 40 kilometres away.
"All I could see was the bright glow. Anybody that lives close by there, it looks like daylight at nighttime," Newnham told CKRM radio.
"They don't want anybody going close by there at all."
The evacuated area is rural. About a dozen people have had to leave.
Burdeniuk said automated equipment shut the facility down on Saturday and Safety Boss, a Calgary company that specializes in putting out oil and gas fires, has been called in to help extinguish the blaze.
He said they have been able to determine the flames are shooting out sideways from the wellhead rather than straight up, which he said indicates some of the wellhead's valve structure may still be in place.
If it is and the valves can be turned off, he said the fire could be out as early as Sunday evening. But if the valves need to be rebuilt, it could be several more days until the fire can be extinguished.
"We want to make sure that when we put this thing out, it's done safely rather than quickly," Burdeniuk said.
Burdeniuk said it appears the flames were sparked when there was a release of gas at the wellhead from one of seven underground caverns at the site. The caverns, he explained, are used to store natural gas for the winter when demand for heating is greater.
The caverns are about a kilometre-and-a-half down and are carved with water in underground salt deposits. Each cavern is about as tall as a 12-storey office building.
Burdeniuk has said he was unsure about whether there was a risk of the gas igniting underground, but said the gas typically burns above ground during such incidents.
He said SaskEnergy has been arranging to bring in water tanker trucks to provide "a wall of water" for the firefighters as they work in the flames.
He noted that water, however, cannot be used be used to put out a natural gas fire.
Air quality testing in the area is "not picking up any contaminants at all ... the flame is burning up all the natural gas." he said.
RCMP said the fire does not appear suspicious at this point.
No one was at the facility when the explosion occurred.
Burdeniuk said the facility would normally be staffed during a weekday, but was designed to be automated on evenings and weekends when demand for natural gas is low. When extremely low temperatures occur, however, he said a staff member sleeps at the site to make sure everything goes smoothly.
No customers have lost service because of the fire, he said.