BP finds leak in valve, begins repairs

BP says a leak has been detected near the top of a new cap designed to stop the flow of oil into the Gulf of Mexico, but it was isolated and being repaired.

The leak was discovered after the oil giant started shutting off valves to test whether the latest fix will stanch the flow for the first time in almost three months.

BP says on its website the leak was in a line that can funnel oil up to a ship if necessary. It shuts off like a dimmer switch.

The other two valves were shut off like a regul ar light switch.

The cap is a stopgap measure designed to keep the oil in the well or funnel it to ships until the relief well is done.

Earlier, BP received the green light from the US government to begin the crucial test that could allow the leaking Gulf of Mexico oil well to be sealed once and for all.

After days of painstaking deliberations, Admiral Thad Allen said he gave the British energy giant the go-ahead after overcoming fears the test could lead to "irreversible leakage" below the seabed.

"At this time we will be releasing an order to BP to proceed with the well integrity test," said Allen, the former US Coast Guard chief leading the government's response to the 85-day disaster.

"This test will run for a maximum of 48 hours at which time we will stand down, assess where we're at, and assess the next steps."

Procedures leading up to the actual test, which included disconnecting the Q4000 and Helix Producer vessels which were collecting oil from the wellhead, were already underway.

In addition, "over 40 ocean skimmers and other assets have been positioned around the wellhead" to help contain the additional oil, the joint command center said, vowing that containment efforts would resume as soon as testing was complete.

The test involves shutting off the valves on a 75-tonne cap installed on Monday to evaluate the integrity of the well bore, which stretches down 2.5 miles (four kilometers) below the seabed.

High pressure readings would allow the three valves to remain shut and the well would effectively be sealed, but low ones could mean there is a hole somewhere in the casing of the well where oil is escaping.

"It will be terrific news if we can shut in the well but I don't think we can say that," Allen said. "I don't want to get anybody's hopes up that we can shut this well in until we get the empirical readings we need."

Allen on Tuesday delayed the high-stakes procedure for 24 hours for further analysis to be conducted, and only made the decision to proceed after meetings with top oil industry experts and US officials, including Energy Secretary Steven Chu, a Nobel Prize-winning physicist.

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