Oil prices extended their slump after data showed the biggest weekly U.S. crude surplus on record, the latest sign of the hurdles facing traders banking on higher prices.

The supply data prompted investors to reduce expectations that two years of oversupply in the oil markets is coming to an end. U.S. prices immediately shed nearly $1 a barrel and losses spread into gasoline and diesel futures.

U.S. crude futures fell $1.33, or 2.9%, to $45.34 a barrel on the New York Mercantile Exchange. Brent, the global benchmark, fell $1.28 a barrel, or 2.7%, to $46.86 a barrel on ICE Futures Europe. Both posted their seventh loss in eight sessions and lowest settlement since Sept. 27.

“You could easily make the argument it’s the most bearish report of all time,” said Bob Yawger, director of the futures division of Mizuho Securities USA. “There’s nothing to support the market.”

The U.S. Energy Information Administration said crude-oil stockpiles rose by 14.4 million barrels in the week ended Oct. 28--the largest weekly increase in 34 years of data collected by the EIA. Analysts polled by The Wall Street Journal expected a more modest increase of 1 million barrels.