Traffic through the Channel Tunnel connecting Britain and France has been suspended after about 100 migrants entered the French side of the complex, the operating company said.
"At around 12.30am, around 100 migrants forced a closure and the entry of security agents into the tunnel," a Eurotunnel spokeswoman said.
"We have suspended the service."
The spokeswoman said police were at the site and that traffic remained suspended.
Ten people, including seven migrants, suffered minor injuries during the storming of the tunnel, a firefighter at the scene said.
The interior ministers of France and Britain signed an agreement in August to set up a new "command and control centre" to tackle smuggling gangs in Calais, as Europe grapples with its biggest migration crisis since World War II.
It came after attempts to penetrate the sprawling Eurotunnel site spiked in August as migrants tried several times a night to outfox hopelessly outnumbered security officials and police.
Thousands of people from Africa, the Middle East and Asia are camped in Calais in slum-like conditions, and at least 13 have died since June 26 trying to cross into Britain, where many have family and work is thought to be easier to find.