LONDON - The only passenger rail link between Britain and the rest of Europe has been shut down indefinitely, Eurostar said yesterday, promising more travel misery for thousands of stranded passengers just before Christmas.

Service has been suspended since late Friday, when a series of glitches stranded five trains inside the Channel Tunnel and trapped more than 2,000 passengers for hours in stuffy and claustrophobic conditions.

Jittery passengers stayed underground for more than 15 hours without food or water, or any clear idea of what was going on - prompting outrage from travelers and a promise from Eurostar that no train would enter the tunnel until the issue is identified and fixed.

Eurostar runs service between England, France and Belgium. The company said yesterday that it had traced the problem to "acute weather conditions in northern France," which has seen its worst winter weather in years.

The company did not go into details, but in a statement it said its program to prepare Eurostar trains for winter conditions had not been adequate and that engineers had to "further enhance the snow screens and snow shields in the power cars of the trains."

The statement said that the fleet was already undergoing upgrades and that more tests were planned for today. A Eurostar spokeswoman said she could not guarantee that service would resume tomorrow.

On Saturday, executives had speculated that the fault lay with the quick transition from the icy cold of France to the relative warmth of the tunnel, which could have produced condensation and interfered with the trains' electrical systems.

Because of the stoppage, 31,000 people in Britain, France, and Belgium had to cancel trips Saturday, and 26,000 more were expected to be affected yesterday.

With a huge backlog of passengers building, Eurostar has blocked any sales until after Christmas.

For those seeking alternative routes between Paris, Brussels, and London, the winter weather was dealing out more bad news.

Nearly half of all flights out of Paris' Charles de Gaulle and Orly airports were cut yesterday through midafternoon, with more cancellations forecast for today. Belgium was also badly hit, with passengers in Brussels lining up for hours to rebook flights.

Tourist Paul Dunn, 46, who was stuck in Paris, said he was looking for alternatives but that information was hard to come by.

"We said: 'Can we get the train to [the French city of] Calais and the ferry?' They are saying: 'We don't know what you can do. You can try.' "

It is a measure of the popularity of the 15-year-old Eurostar service - which whisks passengers from London to Paris or Brussels in about two hours - that its closure has dominated news in Britain.

European parliamentarians on both sides of the Channel have criticized the train company as being irresponsible, while Britain's opposition Conservative Party said the issue was a matter of "huge concern."