Eight people were injured after a Swiss army all-terrain truck crashed head-on into a car on Wednesday in Stein, a town in the canton of Aargau, cantonal police said.

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The incident occurred around 4pm when the heavy-duty army vehicle drove in the wrong lane of the town’s main street and collided with a Peugeot 4007 travelling in the opposite direction, the police department said.

The force of the crash hurled the car backwards into the path of an oncoming Audi A4, police said.

One of three injured occupants of the Peugeot had to be extricated from the severely damaged vehicle by members of the fire department.

Four soldiers aboard the truck suffered “mild to moderate” injuries, while the driver of the Audi was in shock, police said.

All eight people involved in the accident were taken to various local hospitals for treatment.

Police said it is not known why the military vehicle was driving in the wrong lane.

Military justice authorities have opened an investigation into the incident.

The collision disrupted traffic in Stein, which is located across the Rhine River from the German state of Baden-Württemberg.

UPDATE: Military police on Thursday said the driver of the army truck, a 26-year-old recruit, fell asleep at the wheel before veering into the wrong lane.