The decision to kill the animals was made following the discovery that 11 people had been sickened by the same strain found in mink farms and factories.
However, in the haste to dispose of the bodies, Danish authorities reported Thursday that some of the carcasses had risen to the surface of their makeshift graves after gases built up inside the decomposing bodies.
The corpses were buried in military training fields outside the town of Holstebro.
The bodies lay in trenches just over 8 feet deep and 10 feet wide and the first meter of dead mink were covered with chalk before adding another layer underneath the dirt, according to The Associated Press.
Yet, although the mink should have been covered by at least 5 feet of soil, CBS News reported they were only buried about 3 feet deep and also close to a lake — stoking concerns about possible pollution.
Leaders said the grave will be monitored by authorities until a fence can be put up.
The “zombie” mink are being reburied elsewhere and environment officials have promised to fix the situation.
Some mayors have suggested cremating the mink corpses, according to USA Today.
Parliament ordered around 15 million mink to be killed and all mink farming is banned until the end of next year. The country is the world’s largest exporter of mink fur.
Denmark has reported more than 74,700 cases and over 800 deaths, according to data from the Johns Hopkins Coronavirus Resource Center.