French energy company Total has said it has identified the source of its leak on the Elgin platform in the north Sea.
A spokesman for the firm said the leak is from a well into a rock formation about 5,500 metres deep that was plugged a year ago.
However, it is thought that a rock formation above the original reservoir, about 4,000 metres deep, has leaked into the well, sending gas up to the well deck on the platform.
A team of experts from the Total group has been brought into Aberdeen to assess the situation.
The leak was first discovered on Sunday during work by the Rowan Viking drilling rig to abandon the well.
All staff 238 have since been evacuated from the platform and the rig.
Experts from outside the business have also been brought in. Four fire fighting vessels are on standby at the platform, nearby which a gas haze is visible and on which the flare is still burning.
Three options have been put forward by Total to deal with the leak – allowing the gas to dissipate over time, drilling a relief well and or putting well control experts on to the platform.
Total’s nearby West Franklin platform was shutdown at the same time as the Elgin platform.
Shell’s nearby Shearwater platform has also since been shutdown.