A child's body has been discovered in the wreckage of a collision between a truck and bus in south-west France, increasing the death toll to 43.

The crash between the truck and the bus, which was carrying elderly passengers, caused a fire that has also seriously injured four others.

It was France's deadliest road accident in more than 30 years.

Images on French television showed the collapsing, charred frame of the bus engulfed by smoke near the village of Puisseguin, 30 miles east of Bordeaux.

Aerial views showed the mangled remains of both vehicles on a narrow, curving road surrounded by trees.

Eight people, including the driver, escaped after the driver quickly opened the bus door, but others were trapped as flames consumed the vehicles, Puisseguin mayor Xavier Sublett said on i-Tele television.

Among those killed was the truck driver's three-year-old son who was travelling with his father and whose small body was discovered in the truck's wreckage. French media said the truck driver was among the dead.

The mayor told RTL radio the truck driver lost control of the vehicle. The bus driver "tried to avoid it, but the truck came and hit it," Mr Sublett said.

Dr Philippe Flipot of Puisseguin said he spoke to the bus driver afterwards.

"He found himself facing a jack-knifed truck, he couldn't avoid it. He managed to open the doors and some passengers could get off the bus. Risking his life, because flames were licking him, he managed to evacuate some people," Dr Flipot said.

Other authorities remained cautious about the circumstances of the crash. An investigation is under way. The weather in the region was overcast on Friday morning but not rainy.

Prime minister Manuel Valls called the crash the deadliest road accident in France in more than 30 years, and a "terrible shock" for the country.

Police said the death toll was unusually high because both vehicles caught fire immediately. Scores of emergency workers rushed to the scene and helicopters evacuated severely burned victims.

The accident was devastating for the surrounding communities. The bus was carrying members of a senior citizens' club from the town of Petit-Palais-et-Cornemps on a day-long ham-tasting trip to Arzacq-Arraziguet, 120 miles away. The bus had travelled just a few minutes, about four miles, when the collision occurred.

Calling the crash an "immense tragedy," French President Francois Hollande promised an investigation into what happened. Mr Hollande, visiting Greece at the time, also expressed "the solidarity of the whole nation" with the victims' loved ones.