OKLAHOMA CITY (AP) — A natural gas pipeline exploded Tuesday in central Oklahoma, injuring three workers, one seriously, and shooting flames more than 150 feet into the air, authorities said.

Bob Mitchum, 46, was flown by medical helicopter to Integris Baptist Medical Center, where he was listed in serious condition with second-degree burns over 50 percent of his body, hospital spokeswoman Brooke Cayot said.

Fellow workers Danny Fulton and Kevin Venable received minor burns, Cayot said. Fulton, 59, will be held overnight for observation and Venable, 32, was to be released, she said.

The Enogex LLC employees were performing maintenance work on a device that removes water from the line when the pipeline exploded Tuesday afternoon near Pocasset, about 30 miles southwest of Oklahoma City, Oklahoma Corporation Commission spokesman Matt Skinner said.

Flames from one point in the pipeline reached 150 feet to 200 feet in the air before the gas was shut off and the fire dissipated.

Enogex is a subsidiary of Oklahoma Gas and Electric Co. OG&E spokesman Brian Alford said it's not known what caused the blast.

"The fire appears to be extinguished, and we will begin our investigation tomorrow," Alford said.

Valves allowing gas to move through the pipeline were closed, and the excess gas burned off. Alford said inspectors wouldn't be able to get a close look at the damage until the area cools.

Oklahoma Corporation Commission investigators also will investigate, Skinner said. The agency oversees oil and gas production in the state and intrastate transportation pipelines.