Animals on the line at Chalfont & Latimer means that all lines are blocked.
As a result, services between Harrow-on-the-Hill and Aylesbury may be cancelled, delayed by up to 20 minutes or diverted via High Wycombe.
Disruption is expected until 13:30.
Check before you travel:
You can check your journey using the National Rail Enquiries real-time Journey Planner.
Compensation:
You may be entitled to compensation if you experience a delay in completing your journey today. Please keep your train ticket and make a note of your journey, as both will be required to support any claim.