The Channel Tunnel was reopening to freight last night, less than 36 hours after a fire raged inside the rail link between Britain and France, Eurotunnel said.

The tunnel operator said that it had run two test trains through the south tunnel from Calais to Folkestone and was running two more in the other direction. Passenger services should resume at about 6am today, it added.

The blaze was finally extinguished yesterday morning after hundreds of firefighters fought throughout the night to bring it under control.

The tunnel’s closure caused transport chaos on both sides of the Channel, with dozens of passengers stranded and lorries backed up for hours at Dover and Calais.

Four of the 14 people who were injured remained in a Calais hospital last night. Lorry drivers described the chaos as they tried to escape the blaze, which began on Thursday afternoon seven miles from the French entrance.

One said that many had been forced to smash windows in the train to escape after doors became jammed shut. Patrick Lejein, 50, from Bruges, in Belgium, said: “Everything was exploding around us — tyres, fuel tanks — and then there was this smoke which prevented us from seeing and breathing properly.

“The door of our carriage was locked, impossible to open. We had to save ourselves by smashing a window with a hammer.”

A British lorry driver caught up in the fire said yesterday that what he saw had been “hell”.

Leslie Boon, from Pyle, near Bridgend in south Wales, told ITV News that he thought “it was the end” and he might not see his wife and three daughters again.

Mr Boon said: “It was just hell dealing with fire, next minute everyone started jumping up panicking.”

Jacques Gounon, Eurotunnel’s chief executive, said that safety procedures prevented the doors from opening immediately in case there was a risk of anyone being overcome by fumes.

It was confirmed yesterday that some of the lorries contained dangerous chemicals, including phenol.

Timothy Kirkhope, a Conservative MEP and transport spokesman, called for a review of the transportation of combustible chemicals through the tunnel. He said: “Many people will be asking why such chemicals are granted authorisation when even LPG [liquefied petroleum gas] passenger cars are banned for safety reasons.”

A Eurotunnel spokesman said that the carriage of dangerous materials “is very, very tightly restricted, both in terms of the packaging and quantity arrangements”. The company said that it was too early to speculate on the cause of the fire. There were unconfirmed reports that it started in a lorry’s braking system that had overheated and spread to a tyre.

Times recommends

• Britain's top 10 New Year's Day brunches
• Mozambique's lost islands
• The best things to see and do in 2010