Total plans to send a helicopter to inspect its Elgin North Sea platform in the next few days to ensure it is safe before beginning work to cap a well that has leaked explosive gas for more than a week, two industry sources close to the matter said on Monday.

Officials from the French operator of the oil and gas platform are due to meet Britain's Health and Safety Executive on Monday to discuss the risks involved in sending humans to the platform.

All 238 workers have been evacuated and a two-mile exclusion zone set up around the platform for safety reasons, with fire-fighting ships on standby.

Total is sending its own people to ensure the platform is safe...in the next few days, one of the sources said. It was unclear how many staff would take part.

If the operation is successful, Total plans to send experts by the end of the week to the platform to begin injecting mud on the wellhead to stop the gas leak, the sources said.

A Total spokesman said the group was continuing talks with HSE on different aspects of the operation, but declined to comment on any plan to send a helicopter.

The union representing staff at the Elgin platform opposes plans to fly a team of crisis engineers to the platform saying it is too dangerous given the amounts of gas in the vicinity.

We think this is a highly dangerous tactic. Even a dropped hammer could ignite the gas. The whole thing would have to executed perfectly, said a union official who asked not to be identified.

Total has hired a team of international experts to advise it on how to plug the leak, including U.S. firefighting and engineering firm Wild Well Control, which helped tackle BP's Gulf of Mexico oil spill in 2010 and Kuwait's raging oil fires in 1991.

Total will use Canadian CHC Helicopter for its operation, which specializes in the transportation of offshore oil and gas platforms and vessels, the two sources said.

In parallel, the firm has also started preparations for drilling two relief wells.

On Saturday Total confirmed that a gas flare, lit during the evacuation to burn off excess gas, had gone out, reducing the threat of an explosion.

The flare had been burning just 100 metres from the site of the gas leak.

A Greenpeace ship has also arrived near the 2-mile exclusion zone surrounding the platform, the group said. Greenpeace activists collected their first samples of water and air, which will be analysed in Germany.

Danger posed by the gas leak on sea birds and marine plants and animals was small, a marine pollution expert said, due to the low quantity of hydrocarbons contained within the condensates that have formed a slick on the water.

If things continue as they are, I do not think that the marine pollution risks are high. The condensate slick is reported to be slight and diminishing, said Martin Preston, a marine pollution specialist at the University of Liverpool.

Total said to its staff at the end of last week that the gas leak emitted daily carbon dioxide emissions equivalent to a Paris/Shanghai round trip, a source at the company said.

(Additional reporting by Karolin Schaps in London, Marion Douet and Valerie Parent in Paris; Editing by Erica Billingham and Jason Neely)