Story highlights One train's driver is missing after a head-on collision, police say

The head-on crash of two commuter trains happened around 6:50 p.m., spokesman says

It's too early to know what caused the collision in western Switzerland, the spokesman says

The trains were on a route between Payerne and Lausanne, spokesman says

Two commuter trains collided head-on Monday evening in western Switzerland, injuring dozens, officials said.

One locomotive's driver was missing after the crash, police said , and search crews were trying to pry open the train's crushed cab.

At least 40 people were injured, including five seriously, Swiss Federal Railways spokesman Reto Schaerli told CNN.

The collision happened in the village of Granges-près-Marnand, about 8 km (5 miles) south of Payerne, around 6:45 p.m.

Rescue teams at the scene included paramedics, firefighters, police and an air rescue helicopter, police said.

Authorities are investigating what caused the crash.

"At the moment, we don't have any ... information how this collision happened," Schaerli said.

The trains were on a route between Payerne and Lausanne, a city on the shores of Lake Geneva, Schaerli said.

The crash will interrupt train service between Payerne and Moudon -- a city near the line's halfway point -- until at least midnight, Schaerli said.