MADRID, Dec. 22 (Xinhua) -- Emergency services have confirmed 41 people have been injured, four of them seriously, when a local double-decker commuter train collided with the buffers at the station of Alcala de Henares, some 40 kilometers east of Madrid, on Friday afternoon.

The causes of the accident, which happened at around 16:00 hours local time, are as yet unknown, but the train driver has tested negative for alcohol and drugs and it is suspected a failure of the train's breaking system may have been at fault.

Although the train was not travelling at high speed when it hit the buffers, the Mayor of Alcala, Javier Rodriguez Palacios explained there had been a high number of injuries because a high number of passengers were standing up when the collision happened.

The injured have been taken to local hospitals, while Spanish Prime Minister, Mariano Rajoy, has sent a message of support to victims and their families, while Public Works Minister, Inigo de la Serna, has visited the scene.

Spain's railway operator, Renfe, said it was investigating the cause of the crash, adding commuter train service was not suspended. However, some trains were delayed.