Passengers frustrated by delays risked their lives after they jumped from trains and walked down tracks near a south London station.
Southeastern Rail said it was dealing with a "serious trespass incident" after the doors on a train were forced open while it was stopped outside Lewisham station on Friday evening.
Passengers on the train shared footage of people leaving the train and walking back towards the station after they were apparently left trapped just outside the station for at least an hour.
Rail bosses said those involved had been "incredibly irresponsible" as the electrified rail on the track carries "more than enough power to kill".
Power on the train line was turned off, causing further severe delays, while emergency services helped remove people from the tracks.
A Southeastern spokesman said: "We completely understand that passengers on delayed and busy trains may be frustrated, but they simply must stay on the train for their own safety.
"These trespassers risk being electrocuted by the 'third' rail or hit by other trains. They're also causing significant further delay for other passengers that our staff are working hard to get home."
The British Transport Police (BTP) also posted a waning against 'self-evacuation' from stranded trains on Twitter today, saying passengers were "far safer" if they remained on board to wait for help.
"Whilst we totally understand it isn't pleasant being trapped on a train, you are far safer on board," it said.
"Self-evacuating from trains is never a good idea as it places you and others at significant risk."
Network Rail said the Lewisham train had become stuck due to ice on the conductor rail.
Some of those on trains outside the station said they had been trapped for several hours.
British Transport Police said in a tweet that "all available officers" had been deployed to evacuate passengers trapped on trains in the area.
Fire services were also called to the scene.
Mick Cash, leader of the Rail, Maritime and Transport union, said: "Tonight's incidents have once again raised some serious issues about the capacity of Britain's railways to cope with added pressures from adverse weather.
"There must be a full and transparent investigation into the serious issues that have been raised on on transport services over the past week. Warm words from Chris Grayling just won't cut it."
He added: "RMT members are out there working in appalling conditions on our railways tonight and they deserve nothing but total respect and support."
A Network Rail spokesperson said: "At 5.35pm this evening, a train came to a stand near Lewisham Station due to ice on the conductor rail.
"Our team were on site manually de-icing the rail when at 6.45pm passengers began climbing off the train and onto the tracks.
"Safety is our primary concern and the conductor rail in the south east carries 750 volts of electricity, which is more than enough to kill.
"In the event of trespassers on the railway we have to turn the power off for their safety.
"It is incredibly irresponsible and dangerous to trespass on the railway and unfortunately this has meant we have to delay many other passengers who recognise the danger and stay on their trains.
"We worked closely with the emergency services to get passengers back on trains and as of 21.40 we were able to turn the power back on and trains are now able to move again in the area.
"However, passengers may experience residual delays during what has already been a testing day because of the adverse weather conditions for the whole transport network."
Southeastern said it had cleared trespassers from the tracks and restored power by 10.15pm, allowing trains to move again.