Photo: Salta Police

At least 25 people have been killed after a police bus fell off a bridge in north-west Argentina, local media say.

The bus was carrying at least 50 people, most of them members of Argentina’s border police, when it came off the road and fell about 15m (50ft) down a ravine.

Emergency workers are trying to free dozens of passengers who are still trapped.

The cause of the accident is still unknown.

The bus came off the road at 02:00 local time (05:00 GMT) near the town of Rosario del Fuente in Salta province, police officials said.

It was travelling on national highway 34 when the driver lost control of the vehicle as he was coming over the bridge, they said.