He was speaking after talks with leaders of Western allies gathered for a G20 summit in Bali, Indonesia, the Reuters news agency reported.
The explosion on Tuesday at a grain facility in eastern Poland near the Ukrainian border came as Russia fired dozens of missiles against cities across Ukraine in a new wave of attacks targeting critical energy infrastructure, according to officials.
Biden on Wednesday convened a meeting of leaders gathered in Bali to discuss the incident in Poland.
He tweeted: "I’m discussing a meeting with world leaders on the loss of life in eastern Poland and the United States’ commitment to support Poland’s investigation."
Leaders from NATO members Germany, Canada, Netherlands, Spain, Italy, France and Britain took part in the meeting, as well as non-NATO member Japan and representatives from the European Union of which Poland is part, according to Reuters.
Asked whether it was possible to say if the missile was fired from Russia, Biden said: "There is preliminary information that contests that. I don't want to say that until we completely investigate it, but it is unlikely in the lines of the trajectory that it was fired from Russia but we’ll see.”
Biden said in a tweet that he spoke with Polish President Andrzej Duda "to express my deep condolences for the loss of life in eastern Poland and offer our full support for Poland's investigation of the explosion."
NATO ambassadors were expected to meet later on Wednesday.
Meanwhile, initial findings suggested that the missile that hit Poland was fired by Ukrainian forces at an incoming Russian missile, the Associated Press news agency reported on Wednesday, citing US officials it did not name.
The Polish foreign ministry said in a statement on Tuesday that the rocket fell on Przewodów, a village about 6 km from the border with Ukraine.
"On 15 November 2022, another hours-long, massive shelling took place of the entire territory of Ukraine and its critical infrastructure by the armed forces of the Russian Federation," the statement said.
"At 3:40 pm, a Russia-made missile dropped on the village of Przewodów, district Hrubieszów, Lubelskie province, and resulted in death of two citizens of the Republic of Poland," it added.
The Polish foreign ministry also said that Poland's top diplomat Zbigniew Rau summoned the Russian ambassador "and demanded immediate and detailed explanation."
Russia denied it was responsible for the explosion, Reuters reported.
'Most likely Russian-made missile': Polish president
The Polish president told reporters it was "most likely a Russian-made missile," but there was no concrete evidence showing who fired the missile.
The Polish government on Tuesday evening announced that Poland’s armed forces had been put on alert after the incident in the east of the country.
Prime Minister Mateusz Morawiecki said after an emergency meeting of his Cabinet: "Firstly, we have decided to increase the combat readiness of some units of the Polish army, with a particular focus on airspace monitoring. This monitoring will be continued in an enhanced way, together with our allies."
"Secondly, we are conducting analyses and consultations with our allies on the potential use of Article 4 of the Washington Treaty, the article that calls for consultations within NATO," Morawiecki announced shortly after midnight.
He added: "Thirdly, we also decided to summon the Ambassador of the Russian Federation to the Ministry of Foreign Affairs. We are also in constant contact with the Ukrainian government."
Wednesday is day 266 of the Russian invasion of Ukraine.
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Source: IAR, PAP, Reuters