GEORGETOWN, Colo. (CBS4/AP) — Federal investigators are trying to determine why an avalanche shell exploded Monday while state workers were trying to fire a round up a hillside to clear chasms filled with snow near Interstate 70.

An "Avalauncher" (credit: CBS)

An “Avalauncher” (credit: CBS)

Colorado Department of Transportation spokeswoman Crystal Morgan said Tuesday a transportation department worker is in serious condition, and an avalanche forecaster is in fair condition. The federal Bureau of Alcohol, Tobacco, Firearms and Explosives is investigating.

(credit: CBS)

(credit: CBS)

The two men were standing behind a barricade in the area on Loveland Pass about 50 miles west of Denver when the shell detonated prematurely, injuring the men above the waist.

Their names have not been released.

RELATED: 2 State Workers Injured In Explosion During Avalanche Mitigation

The shells are fired using launchers called “Avalaunchers” with compressed gas up mountainsides to set off controlled avalanches to protect drivers and backcountry skiers. CDOT has used the launchers for 30 years without a problem.

“The device was loaded, it was ready to be fired, and it prematurely detonated in the detonation chamber,” Tony DeVito with CDOT said.

CDOT has suspended the use of the Avalaunchers during the investigation and will be using other methods for avalanche mitigation.

RELATED: CDOT Explosion That Injured 2 May Have Been Caused By Faulty Device

The CDOT worker who was injured had 20 years of experience. The crews running the guns pass regular testing to handle the explosives. The Department of Labor has ruled out operator error.

“We believe that it was not due to operator error, but may have in fact been due to the Avalauncher that was in place,” Bill Thoennes with the Department of Labor said. “But we’re not able at this point to say one way or the other.”

In 1991, one person died using an Avalauncher in British Columbia, Canada. The guns are used around the world, and in Colorado they’ve been used frequently this winter because of a weak snowpack. Snowpack specialist Dan Moroz said more blasting will be needed.

“It’s sitting on something really bad. It’s going to go to a 7-Eleven Slurpee,” Moroz said. “So the snowpack is so accumulating, it’s not getting simpler, it’s actually getting more complex.”

In the industry the Avalauncher is seen as the least expensive and safest way to clear possible avalanches. But industry insiders say if the gun is to blame it could permanently change how ski areas and transit authorities clear possible avalanches.

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