It could be late Friday or over the Memorial Day weekend before the world knows if BP's latest effort has succeeded in stopping the surge of oil in the Gulf of Mexico that has already surpassed the Exxon Valdez disaster as the biggest oil spill in U.S. history.
After an 18-hour delay Thursday to assess its efforts and bring in more materials, BP resumed pumping heavy drilling mud into the blown-out well 5,000 feet underwater in a procedure known as a top kill, The Associated Press reports.
BP shares are the top fallers in the London market this morning after the company conceded the cost of its clean-up operation in the Gulf of Mexico is approaching $1bn.
The spill, which has seen oil spewing into the ocean for more than a month after the explosion of BP's Deepwater Horizon oil rig on 20 April, has cost the company $930m (£640m) so far, it told the City this morning. The cost has gone up steadily from the $625m estimate it issued on 18 May, Guardian reports.