Analysts polled by Reuters prior to the data had estimated on average a draw of 3.3 million barrels.
The offshore Gulf of Mexico accounts for about 15% of U.S. oil output and about 5% of natural gas production, according to the Energy Information Administration (EIA).
Oil major Chevron Corp CVX.N evacuated some staff from the region, but production was continuing at the sites its operates in the Gulf of Mexico.
Oil supply is expected to remain tight as analysts expect Saudi Arabia, the world's biggest oil exporter, will extend its voluntary output cut into October.
However, worries about fuel demand and the mixed economic situation in China, the world's biggest oil importer, kept a lid on prices.
Persons:
Lucy Nicholson, Toshitaka Tazawa, Yuka Obayashi, Trixie Yap, Christian Schmollinger, Kim Coghill
Organizations:
REUTERS, Brent, . West Texas, U.S, American Petroleum Institute, Reuters, Fujitomi Securities Co, Hurricane, Energy Information Administration, . Oil, Chevron Corp CVX.N, Capital, Thomson
Locations:
Bakersfield , California, SINGAPORE, U.S, Gulf, Mexico, Gulf of Mexico, Saudi Arabia, Asia, Gabon, China, Tokyo, Singapore