An intruder on the routes between Surbiton and Earlsfield is expected to lead to peak hours for the South Western Railway.
A statement published on the train company's premises states that Network Rail employees and the police are trying to control the situation.
"For the safety of all involved, the power to the track had to be cut off, which means that all lines between Surbiton and Earlsfield are blocked in the direction of London," it says.
"To help you with your trip, your ticket will be accepted at no extra charge for the following services:
- London Underground between Wimbledon and London Waterloo
- London buses between Surbiton / Hampton and London Waterloo
"For more information or referral recommendations, please contact an employee or use a station assistance.
"We apologize for any delay that may arise on your journey."
Initially it was expected that the deals would only last until 7:00 pm, but SWR said they will now last until at least 9:00 pm.