He said the men were unconscious when transported, though he characterized the burns suffered by the younger man as more extensive than those of the supervisor. Both men were confirmed to be in critical condition by Burn Center spokeswoman Marissa Villaseñor.
The exact cause of the explosion was undetermined, though part of the investigation included looking into the possibility that the hot gases engulfed the victims when either a lid was lifted, or blown open by the pressurized gas, on brick-lined steel furnace device.
"We're still in the very preliminary [stage of investigation]," said US Magnesium spokesman Tom Tripp.
He said the injuries occurred as the workers labored to bring a piece of equipment back on line after several days of maintenance work.
US Magnesium emergency personnel quickly responded, providing initial care at the plant's clinic. Tooele County paramedics arrived and took over, preparing the victims for their evacuation in two medical helicopters.
At its plant, about 60 miles west of Salt Lake City, US Magnesium harvests salt from the Great Salt Lake to produce magnesium metal, as well as chlorine, calcium chloride, iron chlorides and hydrochloric acid.
According to various federal, state and company sources, US Magnesium is largest producer of primary magnesium in North America.
It has operated its facilities on the Great Salt Lake since 1972.