Polish authorities say border guards have discovered a small quantity of explosives in eastern Poland, the first such security threat as the country co-hosts the European Championship.

The Interior Ministry stressed Wednesday that nobody was hurt but that leaders have raised a security alert from one to four on a scale of four.

The ministry said the decision was preventative and was only meant to ensure that ''the services responsible for security are on high alert.'' Raising the security level was taken Wednesday at a meeting of a government crisis team attended by Prime Minister Donald Tusk.

Mikolaj Piotrowski, a spokesman for the Polish Euro 2012 organizers, said the explosives were discovered along the Bug River in eastern Poland. He said there was no threat to the football tournament.