A huge steel dome was placed on Saturday over a gushing wellhead on the floor of the Gulf of Mexico in a bid to stop the leak of oil, the U.S. TV news network CNN reported.

The four-storey oil-containment dome, weighing 100 tonne, is to try to cap the oil leaking from the sunken Deepwater Horizon rig and then funnel the oil to connecting pipes leading to the surface.

On Friday, operator British Petroleum (BP) said the capping technique had never been tried at such a depth — 5,000 feet — and there were no guarantees that it would work.

If all goes well, BP hoped to begin sucking the first crude oil through the upside-down funnel and into a waiting tanker on the surface by early next week.

“This is a very large device and it needs to be precisely placed,” said BP chief operating officer Doug Suttles. The never-before-tried procedure would “undoubtedly have some complications” going forward.

An estimated 5,000 barrels of oil are streaming from two leaks every day, posing a huge threat to the environment and fishing industry along the Gulf of Mexico coastline.

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