A municipal bus in Warsaw plunged off a motorway bridge, killing one person and injuring 17, authorities said.

According to the witness half of the bus fell on the road below the bridge, with the front window completely shattered, while the rear half was still on the motorway at the beginning of a slip road.

A large group of firemen and other emergency workers sought to lift and remove the wreckage from the bridge in the hours after the crash.

Confirming the one death in the accident, Health Minister Lukasz Szumowski said five of the injured were in a serious condition. Police were looking into the cause of the accident, which occurred around midday. A Warsaw police spokesman said initial findings suggested the driver, who is now in hospital, may have fainted while driving.