U.S. and Polish officials are investigating the deadly blasts that killed two people in Polish territory on Tuesday. A statement from the Polish Foreign Ministry identified the missile as “Russian-made.” However, Biden told reporters in Bali, Indonesia, where he is meeting with G7 leaders, that there was “preliminary” evidence to indicate that the projectile was not fired from Russia.

“There is preliminary information to contest that [the missile came from Russia],” said Biden. “I don’t want to say that until we completely investigate. But it is unlikely in the … trajectory, that it was fired from Russia. But we’ll see.”

Biden also condemned Russia for escalating its war with Ukraine and launching “scores and scores of missile attacks” on western Ukraine on Tuesday.

The missile that hit inside Poland touched down in the village of Przewodów, near the country’s eastern border with Ukraine. As Poland is a NATO member, the incident sparked concerns that Russia’s war with Ukraine could transform into a new world war.

A NATO official told Newsweek that the organization was “looking into these reports and closely coordinating with our Ally Poland” earlier on Tuesday.

Pentagon Press Secretary Patrick S. Ryder said during a news conference that he would not “speculate or get into hypotheticals” about the missile strike before suggesting that the U.S. would intervene if Russian involvement was confirmed.

“When it comes to our security commitments and Article 5 [of NATO], we’ve been crystal-clear that we will defend every inch of NATO territory,” Ryder said.

Article 5 of NATO requires each of the organization’s 30 member countries to provide military defense to other members if they come under attack from a non-member state.

In comments to the Associated Press, a senior U.S. intelligence official previously confirmed that a Russian-made missile had hit in Poland and killed two people.

However, the missile’s point of origin was not confirmed. The country that fired the missile and the reason for the strike remain unclear. In addition to Russia, Ukraine also possesses some Russian-made missiles.

Russia has denied that its military was involved in the incident and described suggestions to the contrary as “a deliberate provocation.”

“The statements of the Polish media and officials about the fall of ‘Russian’ missiles in the Przewoduv region are a deliberate provocation,” the Russian Defense Ministry said in a statement, according to Russian state-run news agency TASS. “The Russian armed forces did not strike any targets near the Ukrainian-Polish border.”

Newsweek has reached out to the Embassy of the Republic of Poland in Washington, D.C., for comment.