Oil futures dropped toward $40 a barrel on Wednesday to settle with a loss of more than 4% after a U.S. government reported an unexpected weekly climb in crude-oil inventories.

Crude oil for delivery in September settled at $40.80 a barrel, down $1.82, or 4.3% on the New York Mercantile Exchange, with prices marking their lowest settlement since March 2, 2009. The September contract expires Thursday. October Brent crude on London’s ICE Futures exchange also fell $1.65, or 3.4%, to $47.16 a barrel.

NYMEX prices sank after the U.S. Energy Information Administration reported an increase of 2.6 million barrels in crude supplies for the week ended August 14. Analysts polled by Platts forecast a crude-stock fall of 1.2 million barrels, while theAmerican Petroleum Institute Tuesday said supplies declined 2.3 million barrels. The outage at BP’s Whiting refinery in Indiana is “sufficient to push U.S. oil supplies higher over a three-week period,” said Richard Hastings, strategist at Global Hunter Securities. That will increase oil stocks at the Cushing, Okla., delivery point for Nymex futures. BP’s Whiting refinery shut down the largest of its three crude distillation units on Aug. 8 for unscheduled repair work.

Following the supply data, “the trading market will not forgive anything now. Any hint of rising oil inputs and supplies is another reason to sell,” Hastings said. “The bias is lower. The only bulls left are bull ants. They are small.” Gasoline supplies fell 2.7 million barrels while distillate stockpiles climbed by 600,000 barrels last week, according to the EIA. The Platts survey showed expectations for a fall of 1.2 million for gasoline stockpiles and a decline of 500,000 barrels for distillates, which include heating oil.