The explosion came as Russia unleashed a wave of missile strikes Tuesday at cities across Ukraine, hitting residential buildings and knocking out electricity in urban areas. In neighboring Poland, two people were killed in an explosion at a grain processing facility, just a few miles from its border with western Ukraine. President Biden said it was “unlikely” that a missile that caused an explosion in eastern Poland was fired from Russia, but he said the information was “preliminary” and said Poland’s allies would support a full investigation.

Poland’s Ministry of Foreign Affairs said a “Russia-made missile had dropped on the village of Przewodów,” and it had summoned Russia’s ambassador to demand an “immediate and detailed explanation.”Earlier, the Polish government held an emergency meeting to deal with a “crisis situation,” according to a government spokesman, and planned to invoke Article 4 of the NATO treaty, which allows member countries to “consult together” should the “territorial integrity, political independence or security” of any of them be threatened.

President Biden gathered a small group together the heads of G-7 nations as well as the European Union and European Commission for an emergency meeting on the explosion in Poland. Afterward, Biden was asked whether it the missile had come from Russia. “There is preliminary information that contests that,” Biden said. “I don’t want to say that until we completely investigate it. But it is unlikely … that it was fired from Russia,” Biden said, citing the “trajectory.”