An investigation is underway into a deadly industrial accident at one of Tulsa's wastewater treatment plants.
Toxic fumes killed one worker, and critically injured another Tuesday evening. The city says contractors were inside a concrete lined hole doing a demonstration for city workers when something went terribly wrong.
Emergency crews found two men in the hole unconscious. They were overcome by highly concentrated levels of hydrogen sulfide, or sewer gas.
Six people in all were sent to Tulsa hospitals.
Tulsa Fire Captain Adam Balough: "The gas that we're dealing with is a colorless gas, and that's why it can creep on a contractor. What from we observed, the entire area was at a high concentration, so everybody working for the fire department had to have a breathing apparatus."
The name of the worker who died has not been released.
But the company says both of its employees were experienced and had gone through safety training. Investigators say they'll look into how the workers were exposed to such dangerous amounts of gas.