Passengers were left stranded and 24 train services were delayed after a train struck a shopping trolley thrown onto railway tracks on Tuesday.
The British Transport Police has launched an investigation after the driver of a Dorking to London Waterloo service reported hitting the trolley as he passed through Ewell West Station.
As a result, passengers had to leave the train as it was taken out of service for repair, the tracks were damaged, and 24 train services through the area were delayed.
Police believe the trolley may have been thrown from a local footbridge, located about 500 meters away from Ewell West station.
No one was injured in the incident.
Detective Sergeant Tony Samiotis said: "I cannot over-emphasise enough the dangers associated with this type of crime, it is vital that we find those responsible.
"Thankfully this time, through luck, no-one was injured, but we may not be so fortunate if this happens again.
"Trains travel at high speeds and there is a very real risk when they strike objects on the track that they could be derailed.
"We are urging anyone who was in or around that area to contact us if they saw anything suspicious or have any information that may help us with our enquiries.
"If you know who was responsible, or have any information that could assist our investigation, we want to hear from you."
Anyone with information should call the police on 0800 405040, quoting reference B5 of 20/02/13, or Crimestoppers on 0800 555 111.