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Two workers injured in a blast at US Magnesium's Rowley plant in Tooele County remained in critical condition Saturday at University Hospital's Burn Center.

The victims, a 49-year-old supervisor and a 25-year-old worker whose names were not released, were said to be burned over their heads and torsos when hot gases erupted at the plant Friday morning.

The incident was under investigation, but officials said it was possible the explosion occurred when a lid was lifted or blown open by pressurized gas from a brick-lined steel furnace device.

The plant is at 12819 N. Rowley Road northwest of Grantsville, on the western shore of the Great Salt Lake about 60 miles west of Salt Lake City.

US Magnesium emergency personnel provided initial care to the injured men at the plant's clinic shortly after the incident, which was reported to public authorities in a 911 call at 4:45 a.m. Friday. Tooele County paramedics arrived and took over, preparing the unconscious victims for evacuation in two medical helicopters.

Though an investigation was preliminary, company officials said the eruption reportedly happened as the workers labored to bring a piece of equipment back on line after several days of maintenance work.

A spokesperson for Tooele County Emergency Management characterized the burns suffered by the younger man as more extensive than those of the supervisor.

Representatives from U.S. Magnesium could not be reached for comment Saturday.

US Magnesium is the largest producer of primary magnesium in North America, according to officials.