A gunman who opened fire inside a popular nightclub in Florida is dead, police said.
Orlando Police did not immediately provide further details on the department's official Twitter account on Sunday, and it was not immediately clear how the shooter died.
Police described the shooting as a "mass casualty situation" and said local, state and federal agencies were involved in the investigation.
It was not immediately clear how many people were wounded in the shooting, or if any of the victims had died.
Police have told people to stay away from the area and said a noise in the vicinity was a "controlled explosion". No further details were provided on the explosion.
Dozens of emergency vehicles are at the scene around the club.
The club, Pulse Orlando, posted on its own Facebook page just after 2am: "Everyone get out of Pulse and keep running."