A bigger-than-expected build in U.S. crude inventories to fresh record highs pushed oil markets down after an early rally on Wednesday over concerns about production cuts in Canada's oil sands region.
U.S. crude stocks, which have been setting record highs since January, grew 2.8 million barrels last week, government data showed, about a million barrels more than analysts' expectations. Gasoline stocks also posted a surprise increase.
The data overshadowed concerns over evacuations in Alberta, where a wildfire raged unchecked through the city of Fort McMurray in the heart of the oil sands region, prompting some companies, including Suncor Energy and Royal Dutch Shell, to cut back production.
Brent crude futures were down 25 cents at $44.72 U.S. per barrel, after trading as high as $46.01.
Brent has fallen more than 5% from Friday's high in response to rising output from the Organization of the Petroleum Exporting Countries, signs of economic slowdown in the United States and Asia, and a stronger dollar.
While total OPEC output rose in April, outages around the world have been supporting prices. The disruption in Fort McMurray adds to supply losses in Nigeria and Iraq, concern about renewed losses in Libya and fears that Venezuela's cash crunch could hit the OPEC member's output.
