A flame is still burning in the stack above a North Sea platform from which gas has been leaking for three days.
Experts expressed concern that escaping gas could connect with the naked flame in the flare stack and explode.
Oil company Total said a cloud of escaped gas at sea level was at a much lower height than the flare on the Elgin platform, 150 miles off Aberdeen.
A spokesman said the flare was left burning when the platform was evacuated on Sunday.
He said the flare had been doing an important job taking excess gas off the production platform.
It was hoped it would burn itself out but the oil giant did not know when that would happen.
A cloud of escaped gas was reported to have bubbled up through the sea and was surrounding the base of the platform.
A sheen of between two and 23 tonnes of gas condensate, measuring six nautical miles in length, was reported on the water nearby.
The flare was said to be 90 metres (295ft) above the gas leak.
David Hainsworth, health, safety and environment manager for Total, told the BBC that earlier information provided by the company about the flare was wrong.
Mr Hainsworth said that the flare was "still alight", adding "we don't believe it has been reduced in size".
He said he could not put a timescale on the flare being extinguished.
Mr Hainsworth said it was not possible to say whether that would be "an hour, or 24 hours or two days" - or even longer.
He said there had not been time to extinguish the flare when the Elgin platform was evacuated, as the safety of staff had been the priority.
But had there been time they would have considered putting it out, he said.
It was not possible to do that remotely.
Jake Molloy, from the RMT union, said it was "beyond comprehension" that the flare was still burning.
Mr Molloy, who represents offshore workers, said the potential remained for "catastrophic devastation".
Dr Martin Preston, a marine pollution expert at the University of Liverpool, said: "The flare is obviously at the top of the platform and the gas is leaking out round the legs of it so there's some physical separation of a few hundred feet, probably, between the two.
"But obviously if you get a swirl of wind it might raise the gas up higher then it could ignite.
"But it is very difficult to predict and it's obviously going to mean that nobody can get near the platform to do any work until that flare is out.
"It's just not going to be safe. If it just keeps burning then they're going to have to find a plan B. But the plan B which involves drilling a relief well is going to take a very long time."
Oceanographer Simon Boxall told BBC Scotland's Newsnight Scotland programme that the gas would explode if it connected with the flare.
He said: "It would not just go on fire, it would be a fairly volatile explosion."
UK government energy minister Charles Hendry said he had been advised by Total that the flare was "well-above" the level of the gas.
He said: "Clearly, when you have a significant amount of gas escaping, there is a case for trying to burn some of it off to get rid of it rather than leaving it as a hazard elsewhere, so there has to be a decision made on the balance between safe operation and flaring off the gas that can be flared off and closing down the full platform."
Mr Hendry said the government was "very comfortable" that Total had been exercising the emergency plan as agreed.
Mr Hendry said the first concern had been to remove workers and then activate an exclusion zone.
He said they would now move on to trying to "remediate" the problem.
Exclusion zones have been put in place around the platform.
Coastguards said shipping was being ordered to keep at least two miles away and there was a three-mile exclusion zone for aircraft.
Shell has moved 120 non-essential staff from the Shearwater platform and Hans Deul drilling rig, about four miles from the Elgin, because of the drifting gas.
Shell later said it was bringing forward plans to carry out maintenance at Shearwater.
The Scottish government said ministers were being kept "fully informed of developments".
Scottish Environment Secretary Richard Lochhead said: "Any gas leak on an evacuated offshore installation is, of course, deeply worrying.
"Therefore it's critical both Total and the UK government ensure absolute transparency, with all information placed in the public domain.
"This should include not just details on the level of risk, but also how this is calculated."
He said the Scottish government was responsible for the marine environment.
"The gas condensate is expected to disperse naturally and - as the situation currently stands - environmental risks are minimal," Mr Lochhead said.
"However, we're not complacent and are continually reviewing the situation."
Total said it was looking at several options to stem the flow of gas following Sunday's incident.
Earlier, it revealed it could take six months to drill a relief well to stop the leak.
The Elgin platform was not a deepwater drilling rig and platform but it was unusual in that they were drilling down 5km (3.1 miles) into the sea bed.
All 238 workers were removed from the Elgin installation and the nearby Rowan Viking drilling rig by helicopter on Sunday.