TOWER, Minn. (WCCO/AP) — A $50-million physics laboratory operated by the University of Minnesota is being threatened by a fire burning deep in the Soudan Underground Mine State Park near Tower.

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The Department of Natural Resources says no one has been hurt in the fire, which broke out Thursday evening with no one inside the mine. The DNR says the fire isn’t a risk to nearby towns or the environment, and historic buildings above ground are safe.

The DNR said the damage inside the mine due to the fire is expected to be “extensive.”

The onetime mine is now operated as a state park. It’s also the site of physics experiments by the University of Minnesota.

The fire is believed to be burning between the 23rd and 25th levels of the mine. The $50 million Soudan Underground Laboratory is on the 27th level, near the very bottom.

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Minnesota Interagency Fire Center spokesperson Carson Berglund says the power has been turned off, which means the water that naturally drains into the bottom of the mine isn’t being pumped out. If it gets high enough, it could flood the lab.

He says that could happen in one to two days.

In February, WCCO-TV reported on the water discovered at the bottom of the mine, which is believed to possibly be from an ancient sea. The ancient water is seeping from holes that were drilled long ago by miners. Some of the water bubbling out has three times the amount of salt as ocean water.

The only other place they’ve discovered something similar to this ancient water is in the very deep gorges in the ocean floor.

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