PUISSEGUIN, France — French investigators yesterday began identifying the 43 victims of a horrific coach crash, while combing the burnt wreckage for clues to what caused the country’s worst road accident in three decades.

A coach carrying members of a pensioners’ club on an excursion collided with a lorry and burst into flames on Friday near the village of Puisseguin, among the vineyards of the Saint-Emilion area near Bordeaux, plunging southwest France into mourning.

President Francois Hollande’s office said he will lead a memorial on Tuesday for those killed in France’s deadliest crash since 1982, in the tiny nearby village of Petit-Palais-et-Cornemps, where many of the victims came from.

The ferocity of the blaze reduced the coach to a charred shell and police experts say DNA tests and dental records will be needed to identify the victims, many of whom were burned alive.

Officials said the identification process could take up to three weeks.

Four bodies — those of the lorry-driver and his three-year-old son, as well as two of the bus passengers — were removed from the wreckage and transferred to a morgue in Bordeaux.

At the scene of the collision, around 20 investigators in white overalls pored over the remains of the two vehicles. More specialists are expected to arrive on Monday to probe the crash, including why the fire spread so quickly.

Only eight people managed to escape, including the coach driver. One survivor told yesterday of the horrifying speed with which the blaze took hold, and of the desperate efforts to rescue people from the burning vehicle.

“The fire broke out straight away — it was like lightning,” retired carpenter Jean-Claude Leonardet, 73, told Le Parisien newspaper.

“We went back to pull two people who were trapped on the stairs and couldn’t get out. We couldn’t go back there — the fire and the smoke were overwhelming.”

In the absence of bodies, 43 white roses were laid out at the local mortuary in symbolic tribute to the victims.

Investigators will study the lorry’s tachograph, a type of black box that records the vehicle’s speed and journey time, for clues.

But Ghislain Rety, police colonel in the Gironde region, warned it was in a “very, very damaged state”.

“It’s too early to say if it will be usable,” he said.

The wreckage of both vehicles will also be examined to try to establish the circumstances of the crash.

The specialists’ work has similarities with the identification of air crash victims, and some of the investigators worked on the Germanwings disaster that killed 150 people in the Alps earlier this year.

The experts must still determine exactly how many passengers were on the coach as the only official list was on board and burned in the fire.

The pensioners had been heading south to the nearby region of Landes to visit an outlet and museum specialising in Bayonne ham, a local delicacy.

In Petit-Palais-et-Cornemps, with a population of just 756, residents seemed overwhelmed by the tragedy, gathering in the village square to console one another.

“We are here to help our friends who are still here, our friends who are left,” said Gerard Garem, 70, who lost a number of friends in the crash.

“We have no words to say.”

The crash is the deadliest in France since August 1982, when 53 people including 44 children were killed in a motorway pile-up in the eastern Burgundy region.

The lorry driver was identified as a 31-year-old man from the village of Saint-Germain-de-Clairefeuille in northwestern France, where locals said they were stunned by the tragedy.

“We are devastated,” local councillor Luc Bouvier told AFP by phone. “In this village everyone knows each other. We’ve all been talking about it but we don’t know what to do to help.”