The missile that fell in Przewodow, close to the Ukrainian border, was not fired by Russia, according to the country.
Poland claimed it was built in Russia, but according to US authorities, preliminary research suggests Ukrainian air defences shot it.
According to Kiev, more than 90 Russian missiles were launched against Ukraine on Tuesday.
Some of the missiles struck Lviv, which is close to Ukraine’s western border with Poland, even though the military claimed 77 were shot down.
Two Polish labourers were killed in a blast at a farm building in Przewodow, 6 kilometres (4 miles) from the border, during the Russian attacks.
The military of NATO member Poland was put on high alert, and on Wednesday morning, an emergency conference of NATO ambassadors was scheduled to discuss their response.
President Biden informed reporters at the G20 summit in Bali that “preliminary intelligence” contradicted the first claims, which Russia had denounced as a “provocation.”
Western leaders at the Bali summit issued a declaration denouncing Russia’s “barbaric missile attacks” on the towns and civilian infrastructure of Ukraine and pledging their unwavering support for its neighbour Poland.
President Biden, UK Prime Minister Rishi Sunak, French President Emmanuel Macron, and EU Commission President Ursula von der Leyen were among those in attendance.
Dmytro Kuleba, the foreign minister of Ukraine, stated previously that any assertion that Ukraine was to blame for the killings of Poles was a “conspiracy theory” from Russia and that anyone propagating the accusation was disseminating “Russian propaganda.”
Andrzej Duda, the president of Poland, told reporters that the cause of the explosion remained unknown and that investigators were looking into all possibilities.
“As of right now, we don’t know for sure who fired out this missile… It was most likely a Russian-made missile, although the exact origin of the missile is still being looked into “said he.
Images from the Polish farm showed a farm trailer lying on its side and what seemed to be a sizable crater, both of which suggested missile damage. A missile fragment was depicted in a different picture.
Jacek Siewiera, the director of Poland’s National Security Bureau, stated that his country was “verifying the situations in which we might invoke Article 4” of the NATO treaty. Member states may consult under Article 4 to determine whether a member state’s security, political independence, or territorial integrity is in danger.
Nato has been cautious not to get too deeply involved in the crisis in order to prevent an escalation, while providing assistance to Ukraine since Russia’s incursion.
António Guterres, secretary general of the United Nations, also expressed his “great worry” at the explosion in Poland and demanded a thorough investigation.
His spokesman, Farhan Haq, declared that it was imperative to prevent the situation in Ukraine from escalating.
There are a lot of plausible explanations for the incident, according to Paul Adams of the BBC, but Russia had no desire to attack Polish farmers.
It was probable that one of the missiles fired was thrown off course because Ukraine’s air defences had been working hard to shoot down Russian missiles, he added.
The majority of the rockets fired by Russian forces, according to Ukrainian President Volodymyr Zelensky, were intended against the nation’s energy infrastructure.
Andrzej Duda, the president of Poland, held a conversation with Nato Secretary General Jens Stoltenberg, who added that the military alliance was “watching the situation.”
He tweeted, “Allies are closely consulting.” “It’s important to establish all the facts.”