VIENNA - Two trains collided head-on Monday in Vienna, leaving five people seriously injured, Austrian Federal Railways said.

The accident occurred at 8:45 am (0745 GMT) in the Penzing district, western Vienna, according to Austrian Federal Railways. Another 20 people have light injuries, it said.

Austrian rescue personnel carries an injured person in front of two demolished S45 trains after a train crash in Vienna January 21, 2013. Two trains collided Monday morning, injuring 25 people, police said. [Photo/Agencies]

Rescue efforts involved dozens of volunteers and two emergency helicopters and the last passengers were able to leave the train at 10:30 am. (0930 GMT).

One passenger was reportedly stuck following the crash, and some passengers were suffering from shock.

Cause of the collision is still unknown. An Austrian Federal Railways spokeswoman was quoted by the APA news agency as saying that they would "try to clarify the cause of the collision, but for now the focus is on the care of the passengers."