Traffic resumed through the Channel Tunnel connecting Britain and France early Saturday, several hours after being suspended when at least 113 migrants tried to get into French side of the tunnel, the company operating it said.
Scores of migrants clashed with staff and police and forced the suspension of rail services, a spokesman for Eurotunnel said.
The disruption was the latest in a series of incidents involving migrants who are camped around the northern French port of Calais in the hope of reaching Britain.
A spokesman for Eurotunnel said the migrants broke into its French terminal and got onto the tracks. Their effort was coordinated and highly organised, forcing the company to call for police reinforcements, he said.
Eurotunnel services for passengers and freight were suspended, and while trains have started running again they are likely to proceed slowly through the Calais area, disrupting normal timetables, he added.
Calais is just one of the hot spots in a wider immigration crisis, as European countries struggle to agree how to deal with growing numbers of migrants fleeing conflict or poverty.