At least 41 Argentine police have been killed in a bus accident in the northern part of the South American nation.

Authorities say the crash happened early Monday while a convoy of three buses with gendarmes officers was traveling near Salta, a city about 932 miles (1,500 kilometers) north of Buenos Aires.

Angel Marinaro, civil defense director for the province, told local station TN that for unknown reasons the driver of one of the buses lost control as the convoy was crossing a bridge.

The vehicle flipped and fell off the bridge, landing about 65 feet (20 meters) below. Local television images show an overturned bus and rescue crews working the scene.

Authorities say the bus was carrying about 60 people, and survivors are being taken to a nearby hospital.