Oil rig explosion

VENICE, La., May 28 (UPI) -- About three times as much oil per day has been spewing from a wrecked wellhead on the floor of the Gulf of Mexico than had been previously estimated.

BP engineers Friday continued the "top kill" operation, in which workers force thick compounds into broken equipment to cut off the oil flow. There were reports Thursday that the process had succeeded but BP says the efforts continue and, once determined to be successful, the well would be cemented over to further seal the breach.

Emergency teams also were drilling relief wells and outfitting a cap containment system. Additionally BP says about 1,300 ships are collecting oil. The company said the overall efforts have cost more than $900 million so far.

Previous estimates determined about 5,000 barrels of oil a day were escaping into the Gulf of Mexico but Thursday Marcia McNutt, the director of the U.S. Geological Survey, reset that estimate to 12,000-19,000 barrels a day. That means about 600,000 barrels of oil have leaked daily since the April 20 explosion, a figure dwarfing the 250,000-barrel spill by the Exxon Valdez in 1989 in Alaska.

An explosion on the Deepwater Horizon oil platform operated by BP killed 11 workers and caused the massive structure to sink about 50 miles offshore from Louisiana. Officials say they believe a faulty blow out preventer led to the buildup of pressure and the blast. The BOP is the device engineers are trying to fill in the top kill operation.

Louisiana officials said more than 100 miles of the state's shoreline showed signs of oil contamination.