Five oil rig workers in Oklahoma are still missing after a gas well explosion yesterday morning, according to Pittsburg County Sheriff Chris Morris.

The blast and ensuing fire occurred at 8:45 a.m. News sources say emergency responders who were attempting to battle the blaze were hampered by several subsequent explosions. The blaze was extinguished by Monday night.

Seventeen employees were rescued. Only one had serious injuries and was flown by medical helicopter to a hospital in Tulsa, officials said.

The well is owned by Red Mountain Operating and is being drilled by Patterson-UTI Energy. Three of the missing are Patterson-UTI employees.

Red Mountain Operating released a statement saying that it was “deeply saddened” by the incident and is providing support for the families of those who are missing.

Emergency teams worked with rig operators to get the well shut and contained, and the well site will remain closed during an investigation into the incident.