Western leaders moved to calm fears of a dangerous escalation in Russia’s war in Ukraine Wednesday, saying a missile blast in Poland was likely an accident, while Kyiv pushed back hard at the idea its anti-aircraft fire was to blame.

Ukrainian leader Volodymyr Zelensky pointed the finger at Russia, but the United States, like NATO, came out firmly in support of Warsaw’s assessment that the deadly missile was probably fired by Ukraine.

Two people were killed on Tuesday when at least one missile hit a village in NATO member Poland near the Ukrainian border, during a mass Russian bombardment aimed at civilian infrastructure inside Western-backed Ukraine.

Both Warsaw and NATO have said the explosion in the village of Przewodow was likely caused by a Ukrainian air defence missile launched to intercept a Russian barrage — while stressing Moscow was ultimately to blame for starting the conflict.

The White House said it had “seen nothing that contradicts” Poland’s preliminary assessment — while also declaring that “the party ultimately responsible for this tragic incident is Russia.”

President Zelensky, however, said Kyiv had seen no proof the missile was Ukrainian, demanding to be part of any investigation and asking for access to the blast site as well as “all the data” on the projectile.

“I have no doubt that this is not our missile,” Zelensky said. “I believe that this was a Russian missile, based on our military reports.”

In the immediate aftermath, the incident sparked fears of a major new escalation in the Ukraine conflict, but by Wednesday President Andrzej Duda announced Poland’s conclusion the projectile likely originated from Ukraine’s own air defences.

Duda said it was very likely that the Soviet-era missile was launched by Ukraine in what he called an “unfortunate accident,” but that the blame lay with Russia because of its attacks on Ukraine.