The University of Michigan -- concerned about problems caused by burrowing groundhogs -- is using dry ice to suffocate the rodents in their dens beneath the school's North Campus.
The Ann Arbor News reports Thursday that officials say the burrowing could undermine the foundations of structures, porches and pavement.
Spokesman Jim Kosteva says groundhogs "are capable of moving a lot of dirt in their digging." He adds that burrows or holes also can become tripping hazards.
Kosteva says traps were being used for catch and release, but workers began finding the traps closed or the animals released after being captured.
Dry ice melts and becomes carbon dioxide gas. Some U.S. cities use it to kill rats.
The Humane Society of Huron Valley calls the practice against groundhogs cruel.
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