A strike has forced the suspension of services through the Channel Tunnel between the UK and France, as hundreds of migrants try to board UK-bound lorries amid the chaos.
Eurotunnel, which manages the crossing, said “protesters” had entered the terminal and started a fire.
Migrants have been trying to board lorries caught in slow-moving traffic.
About 3,000 migrants are estimated to be living rough around Calais, waiting for a chance to cross the channel.
Lorry drivers have been advised to make sure all their doors are padlocked, to stick with other drivers and not to stop within about 60 miles (100km) of the port.
Workers from the MyFerryLink company had previously blockaded the port of Calais in a protest over job cuts.
The strike is preventing ships leaving or entering the port and the Eurotunnel disruption has left long queues building on the roads into Calais.
The Eurostar train company, which uses the tunnel, said it was “currently unable to run any trains because Eurotunnel has been closed following a fire caused by MyFerryLink demonstrators”.