Merseyrail has revealed what triggered a fire alarm activation at Liverpool Lime Street and Central station.
Passengers were evacuated from the platforms at both stations on Saturday, September 19, after they became engulfed in smoke.
Pictures shared with the ECHO showed smoke billowing up the escalators and masked passengers emerging in a haze.
In a video taken by Arlo Clyne at Lime Street Station, smoke can be seen filling the tunnel as passengers make their way to the exit.
Train services were temporarily suspended from stopping at both stations until early evening.
What caused the incident was initially unclear but it was quickly dealt with.
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In an update on Thursday, Merseyrail told the ECHO that the smoke was caused by a piece of debris.
The debris became entangled with a train travelling into the city centre and came into contact with the electrified line.
This caused smoke to fill the train itself and both stations.
Merseyrail said as soon as they were alerted to the incident passengers were evacuated safely.
Zoe Hands, Chief Operating Officer at Merseyrail, said: “On Saturday afternoon a piece of debris became entangled with one of our trains travelling into Liverpool city centre.
“The item of debris itself came into contact with the electrified line, leading to the smoke that was seen inside the train and station. As soon as this became apparent, all passengers were evacuated safely.
"I apologise for any concern or discomfort caused. If passengers have any particular concerns about the incident, I would encourage them to contact our Customer Relations team at comment@merseyrail.org.”
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Claustrophobic Jen Rowlands, 55, who was waiting for her train back home to North Wales on Saturday with daughter Ela on Saturday, said the experience was "traumatising."
The mum-of-four said she struggled to believe what was happening as "everything changed within a matter of moments."
Jen said a thick cloud of smoke engulfed each floor of the train station and her daughter had to help carry her out.
After the incident on Saturday, Merseyrail tweeted: "Services are now calling at all underground stations following an earlier fire alarm activation.
"Some services may be subject to delay until a normal timetable can be restored."
