The bus which belonged to British company Classic Coaches was carrying young Britons aged mostly in their 20s, who had just finished working during the skiing season. It was travelling down a road from the popular resort of Alpe d'Huez when it hit a cliff face at turn 21at around 1.45pm on Tuesday. It is not clear what caused the accident but investigators believed brake failure was the probable cause.

"It is very probably an issue with the brakes. Now the question is why and the investigation is likely to take a long time," Grenoble prosecutor
Jean-Yves Coquillat told AFP.

According to passenger accounts, the British driver had shouted out that the brakes were not working as the coach hurtled towards the last of a series of 21 treacherous hairpin bends that regularly feature in the Tour de France cycling race.

The driver has been praised for his "remarkable courage" which "saved many lives." Four of the coach's passengers – British seasonal workers – were left seriously injured.

The bus which belonged to British company Classic Coaches was carrying young Britons aged mostly in their 20s, who had just finished working during the skiing season. It was travelling down a road from the popular resort of Alpe d'Huez when it hit a cliff face at turn 21. It is not clear what caused the accident.

"The bus was going down. The driver had time to warn passengers that he had a problem. He hit a parapet and the bus caught fire," said Jean Rampon, an official from the prefect of Isère, the department where Alpe d'Huez is located.

The driver, based in the North East of England died in the crash, four others were seriously injured and 22 more slightly hurt. 

After visiting survivors of the deadly crash at the CHU hospital in Grenoble on Tuesday evening, French junior minister for transport Frédéric Cuvillier emphasized the "remarkable courage" of the vehicle's driver, that "allowed many lives to be saved," French daily Le Dauphiné Liberé reported.

"Every account from everyone we've met confirms that his attitude and his actions prevented the death toll from being heavier," said Cuvillier, who was accompanied on the visit by Britain's Ambassador in France, Sir Peter Ricketts.

Neither Cuvillier nor Ricketts would give details on the sequence of events which led to the fatal accident, nor the actions taken by the driver to minimize harm to the vehicle's passengers. 

"The investigation is now ongoing," Cuvillier simply said, at a press conference on Tuesday evening.

An officer from the gendarmerie told The Local yesterday that claims the vehicles brakes had failed were just "suppositions". Other residents in the resort told The Local they had heard a truck may have been involved.

UK coach operator TGM also confirmed in a statement that the Classic Coaches service was en route from Serre Chevalier to various UK drop off points.

"We are deeply saddened to learn that one of our two drivers on board has died. We are offering our full support to his family and our thoughts are with them at this difficult time. He will be sadly missed by everyone at Classic Coaches," said Heath Williams, managing director of TGM.

“A number of passengers have sustained injuries and our thoughts are with them as they recover.”

“It is too early to say what caused the accident, however, we have launched a full investigation and are working closely with the local authorities.  Our own safety specialist is attending the scene to support the investigation.”

A statement by the Brighton-based travel company Skibound confirmed to The Local that the coach's passengers "had been on their way home after finishing their ski season working for Skibound in various ski resorts across the French Alps." 

A rescue worker described a scene of panic, with many passengers screaming, and reports claimed that at the site of the crash, suitcases lay wide-open next to the charred carcass of the bus with burnt clothes scattered all around.

Three of those who were seriously injured were flown to University Hospital in Grenoble by helicopter, while dozens of firemen and police were dispatched to the scene.

The road leading down from Alpe d'Huez is well known for its 21 treacherous, hairpin bends, and regularly features in the Tour de France cycling race. 

British ski instructor Stuart Adamson from Masterclass British Ski School told The Local: "The resort is in shock. We don't get many fatalities on the roads. French roads are often covered in wreaths where people have died, but not here.

"Its not a notorious road for accidents. Its not a race track, each turn has to be carefully negotiated. Its like an obstacle course."

This aerial satellite photo of a possible route down the mountainside from L'Alpe d'Huez (Point A) to Avenue des Jardins, (Point B) illustrates how sharply winding the descent is.

Tuesday's accident is not the first time this winter that seasonal workers from Skibound have been involved in tragedy at the Alpe d'Huez resort. In January, The Local reported the death of 19-year-old Lucy Sallis from Bognor Regis who drowned in a pool at the resort.   

There have been several deadly coach crashes on the winding roads of the Alps in recent years.

The most serious one was in July 2007, when 26 Polish pilgrims were killed and 14 others seriously injured when their coach – which was on a very steep stretch of road –  crashed into a ravine and burst into flames.

Last September was also a particularly devastating month for coach crashes in France, with two separate bus accidents killing three people – including a baby – and injuring more than 40 others.