SAN FRANCISCO (MarketWatch) -- Natural-gas futures turned lower on Thursday after the U.S. Energy Information Administration reported a slightly larger-than-expected supply increase of 67 billion cubic feet for the week ended Aug. 23. Analysts polled by Platts forecast a climb of between 61 billion cubic feet and 65 billion cubic feet. Total stocks now stand at 3.13 trillion cubic feet, down 235 billion cubic feet from the year-ago level and 45 billion cubic feet above the five-year average, the government said. October natural gas     (ngv13)   was at $3.53 per million British thermal units, down 5 cents, or 1.3%. It was trading at $3.63 before the data.