BP has finally capped the leaking well in the Gulf of Mexico, US officials said Sunday."Additional regulatory steps will be undertaken but we can now state definitively that the Macondo Well poses no continuing threat to the Gulf of Mexico," US official Admiral Thad Allen said.A relief well cut through the original well on Thursday and enabled BP engineers to fill it with cement in a permanent seal.President Obama hailed the announcement and thanked those who had "worked around the clock to respond to this crisis and ultimately complete this challenging but critical step to ensure that the well has stopped leaking forever".The Gulf spillage, the US's worst environmental catastrophe, started following an explosion on the Deepwater Horizon rig on 20 April, which killed 11 rig workers. BP chief executive Tony Hayward was forced to step down due to the size of the spillage, numerous PR gaffes and repeated underestimates of the scale of the leak by the company.The US government insisted the firm put aside $20bn into a fund to pay for costs of dealing with the leak in addition to $8bn spent directly on the clean-up operation. Compensation claims are expected to add considerably to that total.An internal report by BP said that responsibility for the explosion and subsequent leak should be shared by several companies and was due to decisions by 'multiple companies and work teams'. BP accepted responsibility for certain failures, but also said the blame was partly shared by Transocean, the company operating the well and oil service group Halliburton, which was involved in cementing the well.