Thousands of people travelling between and Britain and France faced severe delays on Sunday due to a fault affecting the Eurotunnel train service, a company spokesman said.
Delays of up eight hours have affected 11,000 vehicles, and customers with tickets for Sunday evening were advised to postpone their travel plans until early Monday.
"Eurotunnel apologises for the inconvenience these essential but unplanned repairs have caused," the spokesman said.
Eurostar services, which unlike the Eurotunnel service does not carry vehicles, were also disrupted, the company said.
The fault was fixed late on Sunday but timetables were still disrupted, and extra trains were added to the service to clear the passenger backlog, Eurotunnel said on its official Twitter account.
Normal service is expected from early Monday, and the company will honour the tickets of customers who postponed their journeys, the spokesman said.