A power failure on Monday forced the closure of a section of the track in the undersea tunnel going from France to Britain, spelling chaos for travellers as several Eurostar train services were cancelled.

A spokesman for Eurotunnel, which manages the undersea link, said Tuesday afternoon that the problem had been solved and that the tunnel was once again working at full capacity.

But the delays caused severe disruptions to transport services – particularly to freight links – forcing truck drivers to try and catch ferries in the nearby port city of Calais, only to find themselves grinding to a standstill on a three-kilometre-long (two-mile-long) road leading to the boat terminal.

Many of the trucks were surrounded by dozens of migrants trying to sneak under the axles of the vehicles or into the trailers, forcing drivers to get out of their cabins to try and stop them from getting on board before they passed immigration controls.

Migrant camps have sprung up in and around Calais for several years, and while French police have tried to dislodge them, they have largely been unsuccessful. 

Many migrants hope to hide in trucks or other vehicles crossing to Britain, where they believe conditions are better for would-be refugees than in France.

The power failure in the tunnel on Monday caused a train to stop about a quarter of the way through the 50-kilometre-long tunnel, forcing the 382 people and four dogs on board to be evacuated.

The Eurotunnel spokesman said traffic was now back to normal.

"Repairs took a long time as we had to change 800 metres of overhead lines in this section. An operation over such a distance in a confined space takes some time," he said.