Commuters are facing major disruption at rush hour with trains between Clapham Junction and London Waterloo brought to a standstill.
South Western Railway said they have received an emergency call from a train between the stations and until the situation has been assessed all trains in the area will have to remain at a stand.
Some lines are blocked and staff are being sent to the scene in order to determine what action needs to be taken.
National Rail has warned disruption is expected until 1pm.
Meanwhile motorists are being warned of morning rush hour disruption following a serious crash which has closed the M26 in Kent eastbound between the M25 and the M20.
The motorway was shut following the accident involving a car and a van around 11pm on Tuesday night. A diversion is in place.
Follow latest updates below.
Disruption between London Waterloo and Clapham Junction until 4pm
08:20 , Jacob Phillips
National Rail has warned that there will be major disruption between London Waterloo and Clapham Junction until 4pm.
London Overground routes between Dalston Junction and Clapham Junction are also affected by the issue.
Lines blocked between Clapham Junction and London Waterloo
07:47 , Jacob Phillips
Some lines are blocked between London Waterloo and Clapham Junction due to emergency services dealing with an incident.
South Western Railway have received an emergency call from a train between the stations.
Until the situation has been assessed all trains in the area will have to remain at a stand.
Trains running between the stations may be cancelled, delayed or revised.
National Rail has warned disruption is expected until 1pm.
Severe delays on the Bakerloo Line
07:45 , Jacob Phillips
There are currently severe delays on the Bakerloo Line between Stonebridge Park and Harrow & Wealdstone while Transport for London fix a signal failure.
There is a good service on the rest of the London Underground.
Minor delays on the Northern Line
06:52 , Jacob Phillips
There are currently minor delays on the Northern Line between Kennington and Battersea Power Station due to engineering works finishing late.
Severe delays on the Piccadilly Line
06:51 , Jacob Phillips
There are severe delays on the Piccadilly Line between Acton Town and Uxbridge due to a shortage of trains.
Transport for London has told travellers to use the Metropolitan Line instead between Rayners Lane and Uxbridge.
M26 shut due to ‘serious collision’
06:45 , Jacob Phillips
The M26 has been closed eastbound between the M25 and the M20 due to a serious collision.Emergency services are at the scene and a diversion is in place.National Highways has warned that disruption is expected to continue into rush hour.
