Mendoza, Argentina: A bus overturned in Argentina on Saturday near Aconcagua, the highest mountain outside Asia, killing at least 19 people and leaving 20 injured, officials said.

Operated by the Chilean company Turbus, the bus was traveling from the province of Mendoza toward Chile with 40 people on board when the accident occurred in the Andes region, more than 1,000 kilometers (620 miles) from Buenos Aires.

‘Sixteen people died on the scene and another three in the hospital,’ Oscar Sagas, health undersecretary for the province, told the local news network Siete de Mendoza.

The province’s attorney general, Alejandro Gulle, said that the two Chilean bus drivers, who survived the crash, were held for questioning in the town of Uspallata, a tourist spot near Aconcagua, which at 6,960 meters (22,835 feet) is the tallest peak outside the Himalayas.

The authorities are investigating the cause of the accident, which occurred in the afternoon under good weather conditions and on a well-maintained major road between Argentina and Chile.

According to Turbus, the 40 passengers included 32 Argentinians—three of them children—four Chileans, one Colombian and a Haitian.

The accident happened on Route 7 near Los Horcones, in a spot called the Curva de Yeso, between the Aconcagua Provincial Park close to the border with Chile.

‘It’s a curve that is fairly complicated because of a climb and then a drop,’ Sagas said. Citing witnesses, he said the driver lost control of the bus, which then veered off the road.

One of the children remains in serious condition, and two adults underwent amputations of their left arms due to severe spinal injuries, a medical person at Hospital Central told channel Siete.