TOWER, Minn. (WCCO) –- Firefighters continued to battle the blaze that started in a mine shaft in the Soudan Underground Mine Friday by dumping hundreds of gallons of firefighting foam and thousands of gallons of water down the shaft.

Tower firefighters are hopeful the fire is dying out, according to a report by the Minnesota Department of Natural Resources. As of Saturday morning, carbon monoxide levels in the shaft had dropped, leading firefighters to believe the fire is nearly snuffed out.

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Carbon monoxide is produced during combustion. The lack of carbon monoxide molecules measured in the shaft signals to firefighters that combustion has slowed and that the fire is running out of fuel, the report said.

The water being dumped into the shaft, however, may cause problems.

The Soudan Underground Laboratory, located in the mine, is worth between $50-$100 million and may be damaged if water used to fight the fire seeps into the lab.

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According to the report, experts at the University of Minnesota have calculated that 244,500 gallons of water would need to enter the mine before the laboratory will be at the risk of damage. As of Saturday morning, firefighters had dumped 50,000 gallons of water into the shaft.

Marvin Marshak, a physics professor at the University of Minnesota, said that two important experiments are being conducted in the mine – one on dark matter and another on neutrinos. Both studies seek answers as to how the universe was formed.

Marshak said he is optimistic about the progress firefighters have made.

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At the moment, firefighters are attempting to establish power in the mine to get the sump pumps, which pump 35,000 gallons of water out of the mine a day, running, the report said. However, the firefighters must first figure out if the fire has damaged the mine’s infrastructure and if it is safe to enter, the report said.