Oil giant BP has found a leak in equipment to seal the catastrophic Gulf of Mexico gusher, forcing another delay to the start of crucial tests on a new tighter-fitting cap.
After finally getting the green light to begin pressure tests, BP said it would have to postpone the procedure for a second time to repair a leak in a system of triple blow-out preventers - known as rams - being used in the operation.
It was not immediately clear for how long the leak would delay the tests but it represents another blow to the marathon efforts to put an end to what is already the worst environmental disaster in US history.
On Wednesday, the former US Coast Guard chief leading the government's response to the 85-day disaster gave the British oil giant approval to begin the tests after overcoming fears they 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 Admiral Thad Allen, adding that the test would run for a maximum of 48 hours.
Procedures leading up to the actual test, which included disconnecting vessels which were collecting oil from the wellhead, were already under way by the time the latest delay was announced.
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 (4km) 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. A massive pressure shift could send oil shooting up through a new leak on the sea floor.
