Oil spill 'largest in US history'
3 August 2010 Last updated at 06:09 BST
US government scientists have said around 4.9 million barrels of oil leaked from an oil well in the Gulf of Mexico before it was capped last month, making it the largest accidental oil spill in history.
BP will begin testing on Tuesday to see whether it can permanently seal the leak with mud.
The BBC's Steve Kingstone reports.