An investigation is under way today to try and discover what caused a fire inside the Channel Tunnel.

The blaze started aboard a flat-bed lorry on a freight train 12km from the UK terminal at Cheriton.

A smoke alarm inside the tunnel went off and 34 people had to be evacuated from 30 vehicles aboard the train. They were led to safety via a service tunnel, which exited on the French side.

A total of 30 firefighters, from stations at the Channel Tunnel, Folkestone, Ashford and Deal and from France were drafted in.

John Keefe, a spokesman for Eurotunnel, said: “We will be looking at the lorry which caught fire and trying to find out what happened.”

All Channel Tunnel services were suspended during the incident, which began at 12.30pm on Monday. Cross Channel traffic, hoping to use the tunnel and those heading for the ferries in Dover, ended up queuing on the motorway as Kent Police implemented Operation Stack.

Lorries were kept waiting between junctions 11 and 12 and other traffic was diverted onto the A20. There were still queues and delays on Tuesday morning.

Following the blaze the chief fire officer with the Kent Fire and Rescue Service Charlie Hendry praised his crews and French firefighters for their response and said the successful operation proved the value of regular exercises.

Ten fire engines and specialist vehicles were sent to the incident. Firefighters wearing breathing apparatus took 15 minutes to extinguish the fire.

Mr Hendry said: “There is no doubt that this incident has clearly proved the value of regular exercises.”