The company responsible for an oil spill in the Timor Sea off the West Australian coast says it has stopped oil leaking from the well.

The West Atlas drilling rig has spewed hundreds of thousands of litres of oil into the Timor Sea since late August.

The rig's operator, PTTEP Australasia intercepted the leaking well on Sunday morning, but the platform caught fire, hampering further efforts to cap the leak.

The company says tens of thousands of litres of heavy mud was used in the fourth and successful attempt to stop the leak but the well is yet to be plugged and permanently secured.

PTTEP says the main fire on the platform has been extinguished but other, minor fires are still burning.

Western Australian Premier Colin Barnett says the oil leak and fire has raised serious questions about the safety of a plan to pipe gas from the Browse Basin to Darwin.

The Japanese company Inpex had intially planned to bring the gas from the Icthys field to an LNG plant in the Kimberley, but negotiations failed with the previous Labor government.

It now plans to pipe the gas more than 800 kilometres to Darwin.

Mr Barnett says he is concerned about the risks involved.

"Well I think you've again got to look at the issue of a pipeline 800 kilometres in length at deep water through geologically unstable part of the world and think is that the safest and best way to process that gas?," he said.

"I would say at face value no, you would bring it onshore at the closest land site."