At least 42 people have died in southern Morocco after a bus drove off a road and plunged into a ravine in the Atlas Mountains.

Authorities say that all the victims are Moroccan, but not all of them have been identified as yet.

"We are still in the process of identifying the bodies, as well as the injured," said a local official.

About 25 people were injured - four seriously - in the accident. Most of them have been taken to hospitals in Marrakech and the rest to emergency rooms in a medical structure near Ouarzazate.

The bus was travelling between the cities of Marrakesh and Zagora when it drove off the main road in a mountainous area about 100km south of Marrakesh, near the town of Zerkten in Haouz province.

The bus fell 500 feet (150 metres), 37 people died in the crash, while a further five died in hospital, according to the MAP news agency.

The cause of the accident is still uncertain and an inquiry has been launched, officials say.

Morocco's King Mohammed VI gave his condolences to the families of the victims and offered to pay for the cost of the funerals.

It was the worst bus crash ever recorded in Morocco, which has a notably poor road safety record.

More than 4,000 people died on Morocco's road last year according to figures released by the transport ministry - up 11.6 percent on 2010.