FBI Director Kash Patel says the agency is investigating a targeted terror attack in Boulder, Colorado.
While he did not provide further details, Patel said in a post on social media: "Our agents and local law enforcement are on the scene already, and we will share updates as more information becomes available."
The Boulder Police Department said it was responding to a report of an attack in the city with report of several victims.
A press conference is expected at 4pm on Sunday local time.
According to CBS News, which cited witnesses at the scene, a suspect attacked people with Molotov cocktails who were participating in a walk to remember the Israeli hostages who remain in Gaza.Â
The attack comes just weeks after a Chicago-born man was arrested in the fatal shooting of two Israeli embassy employees in Washington, DC.
Someone opened fire on a group of people leaving an event hosted by the American Jewish Committee, an advocacy group that fights anti-Semitism and supports Israel.
The shooting fuelled polarisation in the United States over the war in Gaza between supporters of Israel and pro-Palestinian demonstrators.