Dozens of migrants trying to stow away on vehicles crossing the Channel by tunnel between France and England broke through perimeter fences at Calais overnight, temporarily halting traffic, a Eurotunnel spokesman said on Saturday.
The disruption was the latest in a series of incidents involving some 3,000 migrants, mostly from Africa and the Middle East, who are camped around the northern French port in the hope of reaching Britain.
"At around 7 p.m. (1400 EDT) on Friday there were migrants all around the perimeter trying to break through the fences," the Eurotunnel spokesman told Reuters. "There was a lot of disruption."
Both freight and passenger services were temporarily halted during the night but are now running normally, although with some delays due to the backlog, he added.
Eurostar, which also runs passenger trains through the tunnel, though not at night, said its services had not been affected.
Over the past month, the growing numbers of migrants at Calais have also been trying to take advantage of a series of strikes by port workers that have caused long lines of trucks to build up on the approach roads to the port.
Calais is one of the front lines in a wider immigration crisis in which European countries are struggling to agree among themselves how to deal with growing numbers of migrants fleeing conflict or poverty.
Many want to get to Britain because they speak English, have family connections or are convinced they stand a better chance of getting a job there.
France and Britain agreed on Thursday to step up efforts to secure the port and the Channel Tunnel.