An apparent train breakdown in the Channel Tunnel meant Eurotunnel Le Shuttle travellers had to be transferred via a service tunnel.
Dozens of people were reportedly left stranded for hours after a fault on a train from Calais to Folkestone.
Footage emerged showing passengers being evacuated and walking along an emergency service tunnel between the UK and France.
They were eventually transferred to a replacement train and taken to the Folkestone terminal in Kent.
Le Shuttle later told the BBC that a train had not actually broken down, but alarms going off meant investigations were needed.
Le Shuttle tweeted last night: “A train has broke down in the tunnel and we are in the process of transferring customers to a separate passengers shuttle via the service tunnel to return to our Folkestone terminal. We apologise sincerely for this inconvenience.”
The company then added: “We are still operating Shuttles on our remaining line but at a reduced service. We are sorry for this delay.”
Travellers planning to use the service from Calais to Folkestone were then advised not to arrive until after 6am today (Wednesday) due to the earlier fault.