A freight train passing through the channel tunnel was forced to stop after a person trying to reach the UK was spotted on one of the wagons.
The stopping of the train resulted in long delays for the service, on both sides of the channel.
Eurotunnel said that the train stopped near to the tunnel entrance on the Calais side, and added that several people were found after a search by police.
Eurotunnel did not specify how many people they found, and said they had been sent back to France.
People stand near the side of the road in Calais, close to the large camp nearby
A spokesman said: "A suspicion of migrants on a freight train led us to stop and search the train."
"We decided to stop it just at the entrance to the tunnel."
Eurotunnel said they would try to get services back to normal after the unscheduled stop, but the BBC reported that travellers from Dover were faced with an hour-long wait before check-in and a three-hour wait after that.
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The waiting time for lorry drivers was said to be around five hours.
Eurostar services were delayed, a travellers in France were being turned away if they did not have reservations.
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On 6 August, a man was arrested by Kent police near the tunnel's exit in Folkestone, after having apparently walked the tunnel's entire 31 mile length from Calais.
