An armed man is holding a number of passengers hostage on a commuter bus in the Brazilian city of Rio de Janeiro, the BBC has reported.
Footage shot from a helicopter shows the bus stopped across two lanes on the bridge connection Rio with the city of Niterói.
Military police officers, ambulances and a special operations team are at the scene.
At least five passengers have been freed. More than a dozen are still believed to be on board.
Brazilian media say it is not clear if the armed man has made any demands. He reportedly boarded the bus at 05:30 (0830 GMT) and threatened passengers.