All trains between Hounslow and Syon Lane were blocked on Thursday afternoon while the police dealt with an incident near the railway.
Services could not stop at all stations between Barnes Bridge while the emergency services responded to the incident.
Lines have since reopened but National Rail has warned that trains may still be delayed by up to 60 minutes or cancelled. Disruption is expected until 7pm.
Rail passengers are facing a third consecutive day of strike action on Thursday.
Members of Aslef at LNER, TransPennine Express and Northern Trains are walking out for the day following similar action over the past two days at other operators.
LNER will run more than 40 services between London, Edinburgh and West Yorkshire, equivalent to around a quarter of its usual timetable.
Aslef members at 16 train operators are continuing with a week-long ban on overtime which will also cause disruption to services until the weekend.
The Gatwick Express is also not running due to the strike action.
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Live updates
Hour-long delays following police incident near Hounslow
Lines have reopened following a police incident near the railway between Hounslow and Syon Lane but delays may not last an hour.
The disruption has severely affected trains between Hounslow, Twickenham, Weybridge and London Waterloo.
Delays are expected until 7pm.
Lines blocked as police deal with incident near Hounslow
Due to the police dealing with an incident near the railway between Hounslow and Syon Lane all lines are blocked.
Train services running through these stations may be delayed or revised. Disruption is expected until 7pm.
Trains unable to run on London Overground
There is currently no service between Gunnersbury and Richmond while Network Rail fix a signal failure at Kew Gardens.
District Line part suspended
There is no service between Turnham Green and Richmond while Network Rail fix a signal failure at Kew Gardens. However, the rest of the line still has good service.
Severe delays on Piccadilly Line
Passengers are facing severe delays between Acton Town and Uxbridge due to an earlier fire alert. However, there is good service on the rest of the line.
Severe delays on Metropolitan Line
There are severe delays between Harrow on the Hill and Uxbridge due to an earlier fire alert. Good service on the rest of the line.
Travellers on A23 hit by major delays due to crash
Travellers on the A23 have been hit with major delays on South Lambeth Road (Northbound) at the junction of Wyvil Road due to a crash, with single alternative traffic in place.
Woman missed flight to Copenhagen due to Gatwick Airport fire evacuation
Good service resumes on District Line
Good service has resumed on the District Line after it was hit by delays earlier due to a points fault at Parsons Green.
Trains from Greenford cancelled until 12pm
A points failure between Greenford and West Ealing has closed all lines. Trains to and from Greenford may be cancelled, or start and terminate at South Greenford. Disruptions are expected to continue until approximately 12pm.