A recent rebound in oil prices came to an end as the benchmark contract for U.S. crude fell $2.65, or 5 percent, to $50.40. One factor driving trading was a report that U.S. crude inventories jumped by 6 million barrels last week, more than analysts had forecast. Crude prices had rallied 19 percent over the previous four days as producers canceled exploration projects and cut the number of rigs drilling.