A fire deep underground in an abandoned mine on Minnesota's Iron Range continued to smolder Saturday, but there were tentative indications that it was gradually being starved of the oxygen it needs to keep burning.

The fire in the Soudan underground mine threatens both an expensive physics research facility and a unique state park.

According to fire officials, USD 40 million more than was originally estimated, laboratories operated by the University of Minnesota in the mine are worth an estimated USD 100 million.

On Friday, a day after the fire was detected, crews placed a cap atop the mine. In addition, they dumped 500 gallons of fire retardant and 50,000 gallons of water into the mine shaft.

By Saturday afternoon, instruments showed that carbon monoxide levels were dropping underground, an indication that fire-feeding oxygen levels also were dropping because carbon monoxide is a byproduct of combustion.

(Sourced from www.startribune.com)