Part of a roof of a passenger terminal at Roissy-Charles de Gaulle international airport near Paris collapsed early Sunday, killing at least six people and injuring three others, police and the emergency service said.

Part of the roof collapsed at around 7 a.m. (0500 GMT) at Terminal 2E of Roissy-Charles de Gaulle international airport. Tons of concrete and metal fell to ground and were scattered over an area of about 50 meters by 30 meters.

A red alert has been declared, but cause of the incident was not immediately known. Following the accident, the terminal was immediately evacuated and rescue workers were searching for survivors still trapped in the debris.

Terminal 2E, put into operation less than a year ago after at least two construction delays, is used by the country's flag carrier Air France and other international carriers.