Panic erupted on board a train during the Monday morning rush hour when passengers overheard a person "preaching about God and doomsday".
The train was just outside Wimbledon station waiting for a platform to become available when customers evacuated from the train at around 8.40am.
The incident happened not far from Parson Greens station, the site of the bucket bomb explosion which left dozens injured.
Adam Brooks was on board the South Western Railway (SWR) train when someone started preaching, which he explained caused a "stampede" and led to someone opening the doors of the train for people to jump out.
Mr Brooks said: "Alarm raised just outside Wimbledon as train waited for a platform... understandable that people are a little jumpy.
"Person preaching about God and said 'You'd better pray, doomsday is here'."
Mr Brooks added that the "intense" noise of 50 people "stampeding" on a packed train sounded like an aircraft taking off.
Twitter user @Styladelica said: "What a journey - passengers on the front coach evacuated the train after mishearing someone and thinking he was a terrorist."
She added: "The guard reported that there was a person in the front carriage talking about doomsday - woman misheard, panic spread in the carriage causing the doors to be forced open and passengers left the train.
"The guard investigated - people got back on and we're on our way," she said at 9.20am.
Residual delays of up to 60 minutes were expected as services running through Wimbledon station were subject to cancellation or revision, with disruption due to last until 1pm.
An SWR spokesperson said: "South Western Railway's control centre received an emergency call from a driver in the Wimbledon area stating that a passenger got out of a train and onto the track, before it reached the station.
"Because of this it was necessary to turn off the [electrical] current in the area, it has since been restored to most lines, however the London-bound route for suburban trains is still blocked.
"Trains will be delayed, altered and possibly cancelled to manage the overall service."
Some lines have reopened and passengers have been told they can use tickets on London Underground and London buses. Disruption is expected to end by 1pm.
The ongoing disruption follows on from earlier problems at London Waterloo and between Purley and Gatwick Airport.
Engineering works overran near Coulsdon South, which meant commuters faced delays and cancellations between Purley and Gatwick Airport on Monday morning.
Disruption was expected until midday with Gatwick Express, Southern and Thameslink services delayed by up to 20 minutes.
London Waterloo was also hit by a points problem affecting platforms 7-11, some lines have since reopened, but disruption was expected until 1pm while the service recovered.
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