TOULOUSE, France (AFP) - France said on Thursday it would declare a state of natural disaster in the south-west of the country after floods claimed three lives and devastated Lourdes.

Fears the Catholic pilgrimage site could be forced to close its doors to visitors for months receded with the flood waters on Thursday, with church officials insisting that the town's celebrated grotto would be accessible to visitors within days.

But other sites, including the underground basilica, have been left facing a lengthy clean-up operation after the Gave de Pau, the river that flows through the town, burst its banks for the second time in less than a year.

Thousands of tourists have had to be evacuated from their inundated hotels and visits to the grotto, basilica and other religious sites have been suspended since Tuesday.

"As the water has begun to recede, we are discovering bit by bit the extent of the damage," said Mr Mathias Terrier, a spokesman for the Lourdes sanctuaries, acknowledging that it could be months before some of them reopen.

Lourdes is visited by some six million people every year with the numbers in July and August reaching a peak of up to 40,000 every day.

Many of the visitors are severely ill or handicapped, drawn to the town by the belief that its waters have curative powers.

The Catholic Church recognises 68 miracles linked to a town where the Virgin Mary is said to have appeared to a local peasant girl in 1858.

Flooding last October cost an estimated 1.3 million euros (S$2.2 million) of damage but the clean-up operation this time will be significantly more expensive, according to Mr Thierry Castillo, who is in charge of the Lourdes diocese's economic affairs.

"We will need the support of everyone," he told Agence France-Presse.

Although the level of the Pau river had receded significantly, those buildings that were not still under water were covered in mud, making it impossible for church officials to know the full extent of the damage.

Firemen were pumping three metres of water out of the Basilica of St Pius X, an underground church with the capacity to welcome 25,000 pilgrims, which was left unscathed by the October flooding.

The surface of the road between the river and the Church of St Bernadette had been damaged by the waters to the extent that the foundations of the church were clearly visible.

The death toll from the flooding in the southwest of the country rose to three on Wednesday when a 54-year-old woman was found drowned in her Renault Clio in a flooded wheat field, 100m from a road that had been closed to traffic on safety grounds. Two elderly people were swept to their deaths in nearby villages earlier this week.

The flooding in the south-west has largely been the result of a sudden rise in temperatures in the Pyrenees, where cold weather had kept snow on the ground much later than is normal after record falls over the winter.

Other parts of France have been hit by torrential rain or hail which have caused significant damage to some crops, notably vines in the area of the Loire valley where Vouvray sparkling wine is made.

Mr Xavier Beulin, the president of farmers' organisation FNSEA, estimated the damage at up to half a billion euros.

"It could be as high as that because there are nearly 300,000 hectares that have been destroyed," Mr Beulin said.