All Eurostar trains have been cancelled because of smoke in one of the cross-Channel tunnels, the company said.
Eurostar said in a message posted on its website: “We are sorry but we are unable to run any further trains today because Eurotunnel has been closed due to smoke detected in the north tunnel.
“If you were planning to travel today, we advise you to postpone your journey and not to come to the station.”
It said all trains were returning to original stations because the tunnel would be closed until further notice.
It comes as security remains heightened following the fatal terror attacks on the Charlie Hebdo magazine and a kosher deli in Paris last week.
Kent Police said the smoke was caused by a lorry fire.
A spokesman said: “A lorry fire has led to the closure of both bores of the Channel Tunnel.
“The fire was at the French end of the tunnel and is being dealt with by the French authorities. There are no reported injuries.
“However, rail passengers are advised to expect significant delays whilst the vehicle is being recovered and fumes are cleared from the tunnels.”