Engineers raced yesterday to build a giant containment dome in case robotic submarines fail to stop oil gushing into the sea from a sunken rig in the Gulf of Mexico.
British energy giant BP is operating four robotic submarines some 1,500 meters (5,000 feet) down on the seabed to try to activate a blowout preventer that can cap the oil well.
But two days of efforts have yielded no progress and placing a giant dome over the leak is now considered the best solution to ward off the threat of an environmental disaster from the huge slick developing off the Louisiana coast.
"It's a dome that would be placed over the leak and instead of the oil leaking into the water column it would leak into this dome structure," US coast guard spokesman Prentice Danner told AFP.
"They started working on the fabrication of this dome structure fairly recently and its estimated it will take two to four weeks to build," he said.
"This is the first time this has ever been done. This idea didn't exist until now. It has never been fabricated before."
The Deepwater Horizon rig, which BP leases from Houston-based contractor Transocean, went down last Thursday 200 kilometers (130 miles) southeast of New Orleans, still burning off crude two days after an explosion that left 11 workers missing presumed dead.
The spill created a massive slick that can be seen from space and, if the winds change, could threaten Louisiana's ecologically fragile wetlands -- a paradise for rare waterfowl and other wildlife -- within days.