HOUSTON, Jan. 23 (Xinhua) -- Five workers were presumed dead after an explosion ripped through a drilling rig in southern U.S. state of Oklahoma, local police said Tuesday.

"At this time, we have moved from a rescue mission to a recovery mission," said Chris Morris, a sheriff of Pittsburg County, about 210 kilometers southeast of Oklahoma City, the capital city of Oklahoma State.

He told a press conference on Tuesday that investigators are waiting on the scene "to cool down and be stabilized" before they can go in.

The explosion cut through the rig Monday morning. Authorities said 16 people escaped the explosion without major injuries. One person was airlifted to a hospital. The fire was extinguished Monday night.

The drilling rig is owned by Houston-based Patterson-UTI Energy, which has grown into one of the nation's largest onshore drilling and hydraulic fracturing companies.

"Five people were tragically lost in the event," said Patterson-UTI Chief Executive Andy Hendricks. "Our focus right now is supporting the families. This has been a terrible tragedy and a terrible loss."

Patterson-UTI and the natural gas well operator, Oklahoma's Red Mountain Energy, said they are working with local authorities and the U.S. Occupational Safety and Health Administration to investigate the accident.

Patterson-UTI has about 25 drilling rigs active in Oklahoma, second only to Texas, where it has nearly 60 rigs in operation.