US commercial stocks stood at 395.3 million barrels for the week ended April 26, the highest weekly inventory figure since the US Energy Information Administration began collecting the data in 1982.
The build comes as US crude production has taken off on the rise in exploitation of shale oil and gas deposits.
It's just indicative of these shale plays ramping up," said Matt Smith, an analyst at Schneider Electric, an energy management firm. "It tells us we're in the middle of an oil boom."
During the same period, US domestic consumption slipped 2.7 per cent to 18.3 million barrels, data show.
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This week's rise in oil stocks of 6.7 million barrels came in well above the 800,000 barrels forecast by analysts, according to a survey by Dow Jones Newswires.
That sent the New York oil price tumbling further after an early fall ahead of the data release.
West Texas Intermediate futures for June delivery were down USD 3.07 to USD 90.39 a barrel around 2100 IST.
The rise in inventories comes amid doubts about the strength of the global economic recovery following mixed economic data in the US and China and a poor performance in Europe.
Central banks have counteracted this trend with aggressive economic stimulus measures. The US Federal Reserve is expected to maintain its current programme of quantitative easing when a key policy committee concludes a two-day meeting later today.