Passengers using the shuttle to cross the channel from France to England are facing hours of delays following a brief suspension of services due to migrant activity at the French side of the tunnel.
Those booked to take their vehicle to the continent are being warned of an hour delay to check in and a further four hours before departure, Eurotunnel said on Saturday.
The operator suspended services for a brief period shortly before midnight due to “migrant activity”, adding that French authorities were dealing with the situation.
It tweeted: “Please be assured we always work hard to maintain the highest levels of security at our Calais terminal.
Le Shuttle, which takes passengers across the channel in cars, caravans, buses or other vehicles, usually operates up to four crossings an hour.
All services for Saturday are sold out, the website shows.
Journeys from France to the UK are now running on time, with three departures every hour, but passengers in Folkestone are facing waits of up to five hours.
Replying to a passenger hoping to cross on a service just after midday Eurotunnel said: “It’s not easy to estimate how long the delays will take to resolve. We’re all doing our best.”
The first Eurostar service, which carries passengers only, departed on time at 6.18am with all other services running on time, according to its website.
Migrants invading the Eurotunnel terminal in Coquelles has become a nightly occurrence.
There were delays to the service on Thursday when the body of a suspected migrant was found on the roof of a Eurotunnel train at the Chunnel terminal in Folkestone.
The news came as video footage emerged apparently showing migrants travelling to Britain on empty freight train carriages.
An estimated 5,000 migrants displaced from countries including Syria, Libya and Eritrea are now believed to be camped in and around Calais.
Freight transport chiefs said Britain’s freight industry is losing £750,000 a day because of the huge problems lorry drivers have faced this summer trying to cross the Channel.
Irish hauliers have also expressed concern over delays and the possibility of being prosecuted if migrants manage to stow away on their trucks.
Operation Stack - where freight traffic is queued on sections of the M20 when cross-Channel services are disrupted - remains in place, and Kent Police warned it could continue until at least tomorrow.
Philip Gomm of the RAC Foundation said: "Kent is a major gateway to and from Europe but once again that gate is well and truly shut.
Operation Stack has become the rule rather than the exception, and on one of the busiest travel weekends of the year it is causing mayhem for hauliers, holidaymakers and local residents alike.
“A few months ago the Government created a new road user watchdog called Transport Focus and it is good to hear it has made Operation Stack its number one priority.
“Solving the immigration crisis is clearly a job for heads of government but that doesn’t mean officials here can’t do more to keep South East England moving.
The depressing thing is that cross-channel disruption is nothing new and Operation Stack has been with us for almost 30 years. Yet only now are we seriously considering how to address its shortcomings.”
Mr Gomm continued: “There are clearly safety issues connected with setting up a contraflow on the M20 or allowing cars and stationary lorries to mix on the motorway, yet there are also health, safety and economic issues associated with local residents not being able to get to work, to the shops or to a doctor’s appointment.
“The idea of widening the M20 to create a spare lane might seem radical, but recent weeks have shown that radical is what we need if people aren’t to be routinely caught in gridlock. Certainly it should be pursued in principle while some of the other immediate, practical suggestions are attempted.”
PA