The US Geological Survey said yesterday that as much as 12,000 to 25,000 barrels of oil had been spewing from the well every day - far greater than the 5,000 barrels a day that had been widely cited. That means that as much as 39 million gallons may have leached into the Gulf of Mexico since the blast on 20 April, compared with the 11 million gallons spilled in the Exxon Valdez disaster in 1989, the previous worst US oil spill.