Eurotunnel says it hopes services will get back to normal soon, after a group of more than 100 refugees broke into its terminal at Calais.
A “large and co-ordinated” group broke onto the tracks at Calais according to Eurotunnel.
It is reported that a number of Channel tunnel staff and two police officers were injured during the incident.
Up to 100 people are believed to have been arrested.
A Eurotunnel spokesman said: “It’s a massive invasion and intrusion by a very large and co-ordinated group of migrants. They are being gathered up by the police authorities.”
“The large migrant group is now out of the way,” he added. “The police have removed them and taken them into custody.
“This is unseen before and a very determined and clearly organised attack with no fear of security forces or police.”
It is believed around 200 people tried to storm the tunnel but 80 were held back by security staff.
The area where the break-in occurred is currently having high security fencing installed, Eurotunnel said. “Police officers were sent into the tunnel to prevent the group crossing to the UK,” the spokesman continued.
Thirteen migrants have died trying to reach Britain since the start of the crisis in June.
An Eritrean man in his 20s, was killed on Wednesday and is believed to have been hit by a freight train near the tunnel entrance at around 1am.
Early on Tuesday morning a 20-year-old Iraqi man was crushed to death after apparently sneaking on board a lorry to reach the UK. The HGV driver discovered the body in the back of his vehicle near Calais port as he inspected his load after he was forced to brake suddenly.
An estimated 5,000 migrants displaced from countries including Syria, Libya and Eritrea are believed to be camped in and around Calais. At its peak, the number of attempts to board lorries or trains was around 2,000 a night, but that has since fallen.
The crisis in Calais is part of a wider migrant surge in to Europe from countries in North Africa and the Middle East.
Services have now resumed after being suspended for nearly nine hours overnight.
It's advising passengers to check in as normal.