Nine Colombian soldiers were killed and 20 others injured when their vehicle plunged into a ravine in southwest Colombia, officials said Monday.

The military vehicle, carrying 36 soldiers, lost control after its brakes failed late Sunday and fell into a chasm about 100 meters (328 feet) deep, according to Luis Alfonso Escobar, governor of Narino department, speaking to Blu Radio.

A video released by authorities showed rescue workers using ropes to reach the wounded at the bottom of the gorge.

Those with serious injuries were airlifted to hospitals, and an army report later confirmed that 20 soldiers were receiving "specialized care."

Initially, officials reported eight soldiers dead and 16 injured.

The soldiers were en route to Narino, a department on the border with Ecuador, to participate in security operations in a region plagued by cocaine trafficking.

Escobar clarified that the accident was not the result of an attack, amid rising violence in Colombia as the country grapples with over six decades of armed conflict. Armed groups are fighting for control of the region, which is key to cocaine production and trafficking.