Authorities in Finland suspect that around 1.3 million kilos of contaminated animal raw feed material was illegally brought to the country from Denmark.
Finnish Customs announced on Tuesday it was wrapping up a probe into the exceptional case.
The agency said a Finnish animal feed producer based in Ostrobothnia is suspected of having imported the contaminated material, fish waste, into the country.
Customs and the Finnish Food Authority reported that the batch had been found to carry the risk of spreading coronavirus and other zoonotic diseases.
Sanna Toivonen, of the Finnish Food Authority, said there was a clear risk of contagious zoonotic diseases spreading from the fish waste.
Authorities suspect the raw material came from Danish fur farms and stored in the same premises where mink carcasses that died from Covid were kept. In Denmark, approximately 17 million mink were culled after some of the animals were infected with coronavirus in 2021.
Director of Enforcement at Finnish Customs, Hannu Sinkkonen, said there had been no similar investigation in the EU prior to this case. He added that the company suspected of smuggling the material was aware of the potential disease risk it carried.
"Such a practice is dangerous for the entire food supply chain," Sinkkonen said.
The Finnish Food Authority asked Customs to investigate the case late last year.
After Customs completes its preliminary investigation in the autumn, the case will head to the National Prosecution Authority for consideration of charges.