Almost three-quarters of the oil spilled in the Gulf of Mexico has been cleaned up or broken down by natural forces. The US government has said in a report that only a quarter of the oil from the BP well remains and that it is degrading quickly. The majority has been captured, burned off or evaporated, it stated. But more clean-up is necessary, officials warn.The report was released after BP announced encouraging progress on its static kill effort to seal the leak. 25 government and independent scientists compiled it.President Barack Obama said yesterday that he was pleased that the operation in the Gulf was finally close to coming to an end.