GRENOBLE, France - A bus carrying Polish Catholic pilgrims from a holy site in the French Alps plunged off a steep mountain road, crashed into a river bank and burst into flames Sunday, killing 26 people, authorities said.

Fourteen others were seriously injured in the wreck on a dangerous stretch of road where past bus accidents have killed dozens of people. Firefighters said the bus did not have the special permit required to use the 12 percent gradient road.

Polish President Lech Kaczynski and his French counterpart Nicolas Sarkozy traveled to Grenoble late Sunday to meet with the injured. Sarkozy said he was "shattered by the scale of the tragedy" and pledged to follow "very closely" the investigation into the causes of the accident.

Local residents said the bus missed a 90-degree bend in the steep mountain road near the village of Vizille as it returned from the shrine of Notre-Dame-de-la-Salette. The bus plowed through a barrier and plunged 65 feet onto the banks of the La Romanche River, catching fire on impact, firefighters said.

"When the bus was burning, there were injured people inside," said Philippe Baret, owner of the field where the bus landed. "I saw at least six of them who were stuck inside the bus and burned to death before my very eyes."

He said he helped pull injured people and bodies out of the bus before it was engulfed by flames. Victims were evacuated by helicopter to hospitals in the nearby city of Grenoble. Crews searched the river by helicopter and boat for a handful of missing passengers.

All that remained of the bus was its charred frame, with pieces strewn across the river bank.

Forty-three pilgrims died in a crash on the same road in 1973, while 29 people died in a crash in 1975. Buses are prohibited from using the five-mile road without a special permit.

"We can't manage to make this descent safe," Jean-Jacques Defaite, the mayor of the neighboring town of Laffrey, told LCI television.

Although it rained heavily Saturday night, it was warm and sunny Sunday and the road was dry.

Some said the bus' speed could have been a factor in the crash. Grenoble state prosecutor Serge Samuel told France Info that four motorcyclists following the bus said it was traveling about 44 miles per hour before it crashed. Experts would verify the bus' speed, he said.

Polish Foreign Ministry spokesman Robert Szaniawski said the bus carried 50 people, including 47 pilgrims, two drivers and a guide; French media reported it had between 50-60 people.

Local police said the bus driver behind the wheel was killed, while his colleague survived.

Most pilgrims were in their 50s to 70s, but among them were three children -- a 12-year-old and two 13-year-olds -- and several people in their 20s and 30s, said Marcin Szklarski, president of Orlando Travel, which organized the pilgrimage.

The travelers were mostly from the Szczecin area in northwestern Poland, near the German border. They had left July 10 for a two-week visit to famous sanctuaries in France, Spain and Portugal, Szklarski said.

The bus, a 2000 Scania, passed safety checks three weeks ago in Germany, Szklarski said.

Three priests were on board, said the Rev. Slawomir Zyga, a spokesman for the Roman Catholic Church in the Polish city of Szczecin. One called the church in Szczecin after the accident.

"He said he was shaken up and bloody, but alive," Zyga told TVN24. "We have no information on the other two priests."

During his visit to a Grenoble hospital treating some of the survivors, Sarkozy said he had "come to express to the Polish president the solidarity of all the French people in the face of this abominable catastrophe."

Sarkozy and Kaczynski, who flew in from Poland, also visited a Grenoble morgue to pay their respects to those killed in the accident, and Kaczynski also visited the crash site.

The Polish government was organizing a flight for the victims' families from Szczecin to France on Monday morning.

Nestled between Alpine peaks, the Sanctuary of Notre-Dame-de-la-Salette is 5,900 feet above sea level. The complex, built where two children claimed the Virgin Mary appeared to them in 1846, draws Catholic pilgrims from around the world.