Eurotunnel passengers were stranded for hours inside the Channel Tunnel on Tuesday evening after a shuttle train travelling from France to England broke down, according to UK reports.
The company confirmed that a train had broken down and they were in the process of transferring passengers to a separate shuttle service.
Later it advised people not to travel to the terminal, but to arrive after 6am on Wednesday.
Social media were awash with complaints, with photos and videos showing people walking along an emergency service tunnel under the sea.
The breakdown reportedly happened on the 3.50pm Eurotunnel Le Shuttle service which carries vehicles from Calais to Folkestone, a journey that is scheduled to take around 35 minutes.
It forced long delays for other passengers waiting to board.
"Scheduled departure 18:36. We are boarding at 01:20, if we leave by 01:36 it will 'only' be a 7 hr delay," tweeted Dr Manuela Gonzalez-Suarez.
"Just got into folkestone after waiting 10 hours. Boards at calais still saying 4 hour delay. What a joke," said another passenger, using the Twitter name VickyHutchins75.
There were many complaints about a lack of information. Some travellers who followed advice to use an alternative route and take a ferry across the Channel said they experienced further delays waiting to board.
Eurotunnel Le Shuttle blamed a technical fault for the train breakdown and apologised for the delay.