The only rail link between Britain and France was closed indefinitely on Sunday as Eurostar investigated a series of train breakdowns that trapped thousands of people in the Channel Tunnel for hours.
The stoppage meant that about 31,000 people in Britain, France and Belgium had to cancel trips planned on Eurostar on Saturday, and 26,000 more were expected to be affected Sunday.
Eurostar originally said that four of its trains were halted in the tunnel Friday evening. On Sunday the company said a fifth train had also been disabled in the tunnel before being towed to London. A sixth train broke down Friday, although outside the tunnel, 24 miles of which sits under the English Channel, Eurostar said.
Following unsuccessful attempts to move some passengers between London and Paris on Saturday evening, the company has canceled all services "until we get to the bottom of what happened Friday night," Eurostar chief executive Richard Brown said. "We will not start services again until we are sure we can get them through safely," he told BBC television. "We want to understand what it was that caused this unprecedented breakdown."
He added that normal services might not return for days. The company said it had taken the precautionary step of canceling all ticket sales until after Christmas.
The problem is the latest of several that British travelers have faced as the Christmas and New Year's holidays approach.
Several airports have been affected by unusually heavy snow falls.
On Sunday, the runway at Manchester Airport — Britain's busiest outside the London area — was closed for emergency snow clearance. On Friday, Gatwick Airport in London closed its runways for several hours for the same reason. Other regional airports such as Bristol in southwestern England and Belfast in Northern Ireland also were hit by delays and cancellations.
Many other travelers with bookings on British Airways had a close call. Last week, a court blocked a planned strike over the holidays by BA cabin crews, which would have disrupted the travel plans of around 1 million people.
Trapped Eurostar passengers spoke of languishing in the dark for up to 16 hours without adequate food, water or any clear idea of what was happening. Some reportedly suffered asthma and panic attacks.
While most of the trains were towed out, two had to be evacuated, forcing passengers to walk through sections of the darkened tunnel.
French European parliamentarian Dominique Baudis, who was traveling from Paris to London on one of the trains that broke down, said the trip from took 12-13 hours, including six hours in a train inside the tunnel.
Passengers were "without water, without any information and without any help provided to the most vulnerable passengers. There were many children aboard, small children including some just a few months old. There were also elderly people who had trouble getting around," he told France-Info radio. "It's absolutely inconceivable."
Brown seemed to acknowledge that there were some problems on at least one train but defended his staff.
"I'm not pretending it went well. I think it went quite a bit better than people say," he said.
The company is running special trains through the tunnels in a bid to pinpoint the problem, press officer Anelle Mouhaddib said Sunday, with results of engineers' tests expected later Sunday.
Earlier, officials blamed the problems on the quick transition from the icy cold of France, which is suffering some of its worst winter weather in years, to the relative warmth of the tunnel, which could have produced condensation and interfered with the trains' electrical systems. But the exact cause remains unclear.
"It's all a bit of a mystery and the company, and indeed a lot of people, appear baffled by it," said Nigel Harris, the managing editor of Rail magazine. "What is really puzzling about this is the fact that it is happening now, even though the trains have been exposed to cold weather over the last few years."
Comparable trains in France have "been going even longer than Eurostar without experiencing any of these cold-weather problems," he said. The cold weather has had little effect on France's TGV high speed trains, some of which were running with minor delays Sunday because of drivers slowing down on certain sections of track.
Television footage from London's St. Pancras Station showed bleary-eyed passengers waiting in line or scrambling for information about Eurostar. A few were in tears.
The problems — and passengers' complaints about their treatment while trapped on board — could deal Eurostar "huge reputational damage," Harris said. "They have promoted themselves as the 'green,' stress-free alternative to flying and now they face a major technical issue that they need to get on top of."
Eurostar's executives have offered refunds and free travel to those affected by the latest cancellations.