Police in the US city of Lewiston, Maine have warned a gunman is on the loose, with reports that at least 16 people have been killed.
Residents of the city, the second-largest in the state, have been told to shelter in place.
Police said they were investigating incidents at "multiple locations" and released photos of a suspect.
The White House said President Joe Biden had been briefed on the situation and would continue to receive updates.
There were also multiple but unconfirmed reports of at least 50 people injured.
In a statement on X, formerly Twitter, Maine State Police said: "There is an active shooter in Lewiston.
"We ask people to shelter in place. Please stay inside your home with the doors locked."
The Central Maine Medical Center said it was reacting to a "mass casualty, mass shooter event" and was coordinating with other hospitals in the area to treat the injured.
The Androscoggin County Sheriff's Office released two images of a suspect, saying he was at large and asking for the public's help identifying him.
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