Gasoline futures plunged after a surprise uptick in inventories, pulling crude prices downward. The drop was so steep it triggered a rare five-minute halt of all energy trading on the New York Mercantile Exchange for the first time in more than two years.

Options volume was heavy in bearish contract combinations in the SPDR S&P Oil and Gas Exploration and Protection Fund, made up of stocks like W&T Offshore Inc. (WTI), Gulfport Energy Corp. (GPOR) and Petrohawk Energy Corp. (HK), for the third time in a week.

Put volume in the ETF was the fourth highest on record and five times the daily average, trade alert data showed.

One large block of opening investors built positions that profit if the wild swings that have racked the commodities complex in the last week continue through the end of this year. These traders bought $59 "puts" that expire in December while also purchasing $62 "calls" that expire the same month. The move, known as a "strangle," profits only if the ETF rises or falls sharply before the end of the year. The XOP closed down 4.4% at $57.84.

Calls grant the right, but not the obligation, to buy shares at the "strike" price by a set time frame, while puts grant the right to sell shares.

Also on Wednesday, buyers of bearish puts dove into $47 contracts that expire in September.

-By Chris Dieterich, Dow Jones Newswires; 212-416-2611; christopher.dieterich@dowjones.com