QUINTON, Okla.-A Houston-based energy company is confirming five of their employees are missing after an explosion at a drilling rig in eastern Oklahoma.

  

Patterson-UTI Energy Inc. said in a statement Monday that the cause of the fire remains unknown but that some of their employees "are unaccounted for at this time."

  

Pittsburg County Sheriff Chris Morris says five employees remain missing after the explosion Monday morning on the natural gas rig near Quinton, about 100 miles (161 kilometers) southeast of Tulsa.

  

According to the Oklahoma Corporation Commission, the well site is operated by Oklahoma City-based Red Mountain Operating. Patterson is a drilling rig operating company.

  

Pittsburg County Emergency Management Director Kevin Enloe says crews are allowing the fire to burn out to avoid spreading contaminants.