A train carrying about 70 people has derailed after hitting a landslide caused by heavy rain, British Transport Police say.
The incident happened at about midday just north of Merstham tunnel, near Redhill, Surrey, Britain and involved the 10.56am Brighton to London Victoria service.
There are no reports of any injuries although some of the passengers are said to be suffering from shock.
A BTP spokeswoman says officers are at the scene with their counterparts from Surrey Police and local ambulance and fire crews.
It is understood the scene is difficult to reach because of muddy conditions.
"The cause of this derailment appears to be a landslide caused by the recent heavy rain," said the spokeswoman.
"There are approximately 70 people on the train. There have been no reported injuries other than people reported to be suffering from shock.
"The emergency services are concentrating their efforts on the rescue of these people from the scene.
"Once this is completed, the scene will be handed to Network Rail and the Railway Inspectorate to investigate the matter further."