Attackers have torn up 400 genetically modified birch trees in Finland, wrecking the nation's only research into the environmental impact of biotechnology on forests, officials said Wednesday.

Police said they did not yet know who was behind the attack on the Punkaharju site in eastern Finland or whether protesters opposed to genetic modification were involved.

The trees were chopped down or torn up by their roots over the weekend on the fenced but unguarded site.

Some environmental groups fear genetically modified trees might irreversibly contaminate food crops and wild species, an issue the study aimed to investigate.

"The research investigated the possible environmental effects of doing field studies using genetically modified materials. It would have been extremely important to find out about these issues," said research station head Juhani Haggman.

The 400 trees were part of Finland's only field study on genetically modified trees. The forestry industry hopes genetic modification could cut paper-making costs and improve products by producing trees with suitable traits.

"We lack research on how genes work," Haggman said. "We are talking about several hundreds of thousands of euros in losses. The highest estimates that have been aired have been close to a million euros ($1.21 million). Then there's the value the research results would have had," Haggman said.

The crime carried a maximum penalty of a four-year jail sentence, said Detective Chief Inspector Martti Kemppainen, who is heading the investigation.