(CNN)Five oil rig workers were missing after an explosion Monday in an Oklahoma gas well, Pittsburg County Sheriff Chris Morris said in a press conference.
Seventeen employees were rescued but "five are still unaccounted for at the well," Morris said.
Sixteen people had no injuries or minor injuries, and one person was flown by medical helicopter to a hospital in Tulsa, officials said.
Emergency responders received a call reporting the gas well explosion at 8:45 a.m. local time.
The location was on fire, and crews were pulled back after several explosions, said Pittsburg County Emergency Management Director Kevin Enloe.
Emergency teams worked with rig operators to get the well shut and contained, said Enloe. The fire was out by Monday night, officials said. The well site was closed pending an investigation.
The new well is owned by Red Mountain Operating, according to a spokesman for the Oklahoma Corporation Commission, the state's regulatory agency for oil and gas. The well was drilled by Patterson-UTI Energy, said Enloe. It is unclear if crews were drilling for oil or natural gas.
Patterson-UTI released a statement saying it was "deeply saddened" by the incident.
"Our hearts go out to the families of the five missing individuals, three of whom are Patterson-UTI employees," the statement said. "We've reached out to their families and are providing support during this difficult time. At this moment, no one knows with certainty what happened and it would be unwise to speculate."
CORRECTION: This story has been revised to give the correct name of Red Mountain Operating.