Oil prices fell for the fourth day in a row on Thursday, taking losses so far this week to 7.5 percent on burgeoning crude supplies and healthy gasoline stocks in the United States. U.S. light crude slipped 35 cents to $51.26 a barrel, extending Wednesday's near 5-percent drop after government data showed a big rise of 5.5 million barrels in crude inventories. London's Brent crude lost 54 cents to $51.75 a barrel. Signs this week that OPEC exporters have made good a pledge to increase world supplies along with the latest U.S. inventory data have hammered prices, which now stand about $7, or 12 percent, below the record $58.28 for U.S. light crude struck on April 4. In its latest report for the week to April 22, the Energy Information Administration (EIA) put U.S. commercial crude stocks at 324.4 million barrels, 9 percent above a year ago and the highest level since May 31, 2002.