BBC news has the following story
Twenty fire engines have been called to a blaze involving two trains on a section of the high speed cross-Channel rail link which is under construction.
Eurostar said the fire, in the Thames tunnels area, is on a stretch of line being built between Gravesend and St Pancras, London.
One train was pushed from where the fire started in Swanscombe, Kent, along the track to West Thurrock, Essex.
The fire is thought to involve two construction trains.
Police and ambulance crews are at the scene but emergency teams were unable to say whether there were any people on board the train.
A spokesman for Eurostar said the company was not due to use the line until 2007 and that Eurostar services would not be disrupted.
Kent Fire and Rescue Service sent 10 pumps to the fire scene and 10 from Essex attended at about 1920 BST.