Already trading at six-year lows on a prolonged slump, U.S. crude fell $2.21 to finish at $38.24 per barrel. Oil hadn't closed below $40 since February 2009, although it briefly traded below that level on Friday. Monday's closing price was the lowest since Feb. 18, 2009.
Brent crude, a benchmark for international oils used by many U.S. refineries, slipped $2.77 to $42.69 Monday and is at its lowest levels since March 2009.
