Eurotunnel services were hit by delays after migrants were found on French rail track near Calais.
Trains were held up by an hour after the migrants went on to the track in the area around Frethun station.
A Eurotunnel spokeswoman said: "At 2.30pm local time (1.30pm BST) traffic that was exiting our northern tunnel was brought to a stop due to there being migrants on the SNCF track."
Passengers travelling from France to the UK were delayed by one hour, she added. The timetable was expected to be back to normal by 4.30pm BST.
A message on the Eurostar website stated that its services were also disrupted.
On Sunday Eurotunnel customers heading to the UK faced delays of three-and-a-half hours after migrants were spotted on a freight train.