Exclusion zone has been declared around Total platform in North Sea
A two-mile exclusion zone has been declared around Total's Elgin Franklin platform in the North Sea after a cloud of gas surrounded the rig.
All 238 workers have been evacuated from the platform, while 85 oil workers were airlifted away from a nearby rig operated by Shell over fears of drifting gas.
The French company says it is taking 'all possible measures' to bring the leak under control and may drill a relief well to ease pressure.
However, the option could 'take months', says the RMT union.
'People seven miles away can see a gas cloud coming from the Total rig,' Jake Molloy, head of the RMT branch that represents offshore oil and gas workers, told BBC Scotland.
'As far as we can tell, certainly in the UK sector, this is an unknown. It has never occurred before,' Mr Molloy continued.
'One drilling engineer that I have spoken to today says we could be looking at a Deepwater-type intervention, in that we have to drill a relief well from another rig, but even that will be dodgy if we have got gas continually escaping in the immediate region.'
The UK Department of Energy and Climate Change (DECC) said the leak took place 'during work to plug and abandon the well, which was no longer producing gas'.
'Total has now shut in all wells but remote monitoring has revealed that gas continues to be released,' a spokesperson continued.
In 2010 an explosion and subsequent fire at the Deepwater Horizon offshore drilling unit in the Gulf of Mexico killed 11 workers and started an environmental disaster considered the worst in US history behind only the Dust Bowl of the 1930s.