A U.S. official confirmed the strike to the Associated Press Tuesday afternoon, but more details about the strike remained unknown. Polish authorities were holding an emergency meeting due to a “crisis situation” but did not immediately comment on the reports. Polish media reported that two people died after the strike in the village of Przewodów, located near the Poland-Ukraine border, according to the AP.

Poland is a member state of the North Atlantic Treaty Organization (NATO). Any NATO member state may invoke Article 5 in the event of an attack, which would draw an international response from other members, including the United States.

“WWIII” quickly began trending on Twitter amid these reports, with some users raising concerns about the possibility of a heightened military response. However, Poland has not invoked Article 5—and doing so would not automatically trigger World War III.

“I didn’t have WWIII on my list of existential crises this week,” tweeted Colorado Sun reporter Jesse Aaron Paul.

“World war 3 is maybe breaking out and i am here clicking on accounts’ verified checks to see whether they’re officials or twitter blue subscribers,” tweeted Buzzfeed reporter David Mack.

Others encouraged a more patient approach, urging people not to jump to conclusions that the strike will result in escalated military conflict.

“Today’s Twitter Challenge: Do not predict World War 3, and instead let diplomats do their work,” Complexly CEO Hank Green tweeted.

“Important on Article 5. It’s often said that an attack on a NATO ally could ‘Trigger’ an A 5 response but NATO officials really stress that Article 5 is a conversation, not a machine. ‘An Article 5 Response’ can take all sorts of forms. It’s not a WWIII button,” tweeted Defense One editor Patrick Tucker.

Dr. Jennifer Cassidy, an expert on diplomacy, tweeted: “Senior U.S. intelligence official says Russian missiles crossed into NATO member Poland, killing two. Many people now mentioning triggering Article 5. We must ALL keep a calm, and collected head here. Putin wants WWIII. He’s in this war, until his end. We cannot give him that.”

The strikes marked the first time since Russian President Vladimir Putin launched the war in February that missiles have crossed the borders into a NATO member state. It comes after a Ukrainian energy official warned Russia’s latest attacks against Ukraine’s infrastructure could affect the Eastern European nation’s neighbors.

Pentagon Press Secretary Patrick Ryder said on Tuesday U.S. defense officials are aware of the reports and committed the U.S. to defending NATO.

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

Update 11/15/2022, 3:47 p.m. ET: This article has been updated with additional information.