Passengers on an Aylesbury-bound train had to be evacuated after a fire broke out.
The fire started in the exhaust of the 5.57pm service from London Marylebone to Aylesbury on Friday (December 27).
Passengers were evacuated at Chorleywood and firefighters were called to deal with the incident.
Andrew Munden, operations and safety director at Chiltern Railways, said: “The fire service were called and our station staff worked alongside them to ensure all passengers safely disembarked.
“The train has been taken out of service and the cause of the fault is being fully investigated.”