QUINTON, Okla. -- Five people are missing after a fiery explosion ripped through an eastern Oklahoma drilling rig Monday morning, sending plumes of black smoke into the air and leaving a derrick crumpled on the ground, emergency officials said.

Pittsburg County Emergency Manager Kevin Enloe said at least three medical helicopters landed at the site following the explosion. He said about 17 workers were taken off the site following the blast, but that five remained missing Monday afternoon.

CBS News correspondent DeMarco Morgan reports authorities are not letting anyone get close to the site of the explosion Monday night. With fires still burning, searcher have not been able to get closer than 100 feet to the rig to search for the five missing workers

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Aerial footage from CBS affiliate KOTV in Tulsa showed the fire still burning at the site. The heat from the fire caused the derrick to collapse, which spread the flames across the site. The explosion occurred west of the town of Quinton, about 100 miles southeast of Tulsa.

A person who owns land near the drilling site told KOTV the explosion killed cattle in the area.

More than 20 employees were at the well site when the explosion occurred, Pittsburg County Sheriff Chris Morris told The Associated Press.

"Most everybody was taken off the site and taken to a secure site here in Quinton," he said.

Aerial footage of the rig explosion in eastern Oklahoma on Monday, Jan. 22, 2018. KOTV

Morris confirmed that five people were unaccounted for, but he said could not confirm any fatalities or injuries.

Amy Elliott, a spokeswoman for the Oklahoma medical examiner's office, said she wouldn't be able to confirm any fatalities until the fire is extinguished and investigators can get to the scene of the explosion.

"I pray there's not, but we just don't know yet," Elliott said.

Oklahoma Office of Emergency Management spokeswoman Keli Cain said state environmental and regulatory officials have been notified and were heading to the scene. A local emergency dispatcher said the sheriff, undersheriff and county emergency management director are all on the scene.

The drilling site was being operated by Oklahoma City-based Red Mountain Energy, said Matt Skinner, a spokesman for the Oklahoma Corporation Commission, which regulates oil and gas operators in the state. Telephone and email messages left with Red Mountain were not immediately returned.

Skinner said a company that specializes in rig fires and other well control problems also responded to the blaze.