There are delays on train services in and out of London Victoria due to signalling problems at Herne Hill which have resulted in some lines being blocked.
The signal fault has blocked the line towards Bromley South. Network Rail engineers are en route to investigate the problem with the detection system that is used to control the signals, National Rail said.
The disruption is affecting Southeastern services between Beckenham Junction and Victoria.
National Rail said train services running through Herne Hill may be delayed or diverted between London Victoria and Bromley South. Disruption is expected until 9:30am.