RENNES-LE-CHATEAU, France – The mayor of a French village besieged by obsessive fans of “The Da Vinci Code” has been forced to dig up the body of a mysterious priest and encase it in a concrete mausoleum to deter rapacious treasure hunters.

The cemetery has also been closed after tens of thousands of tourists swamped Rennes-le-Chateau, in southeastern France, where a 2,000-year-old local mystery inspired the plot of the best-selling religious thriller.

Legend has it that the area, known as the “Valley of God” and once a remote Roman outpost, conceals a remarkable collection of religious relics and treasures. They are said to range from simple pots of gold to the body of Jesus Christ, the Holy Grail, and the Ark of the Covenant.

Hidden documents are rumored to hold clues that would challenge religious doctrine by proving that Jesus did not die on the Cross but survived, married Mary Magdalen, and fled to France – one of the central claims made in “The Da Vinci Code.”

Until recently the mayor of the village, Jean-Francois L’Huilier, seemed to be winning the battle against fortune-seekers who tried to disinter bodies and dynamite holes in the walls of its 11th-century church looking for relics.

Now, however, Rennes-le-Chateau has become the latest victim of “The Da Vinci Code” fever. Since its publication 20 months ago, Dan Brown’s heady mix of fiction, fact, and legend has sold more than 9 million copies in 42 languages.

“The world has gone mad,” said Mr. L’Huilier. “It’s a well-written book, but it’s a novel, not a historical document. It astonishes me that some readers get to the end and think it’s true.

“It’s a Philistine minority, but they come here and stomp all over the place with no respect for anything or anyone. Last year they even tried to tunnel into the church. It was like something out of a prison escape film. They began digging in the night, put the soil in bags, and put the bags in the hole which they covered with a layer of earth so nobody would see during the day. It was only when someone noticed the flower beds moving that we discovered what they were up to.”

The legends were fuelled in the 1880s when an impoverished Roman Catholic priest assigned to the parish, Abbe Berenger Sauniere, became inexplicably wealthy. Sauniere – whose name is shared by one of the protagonists in “The Da Vinci Code” – set about renovating the church, which is dedicated to Mary Magdalen. Above the door he installed a stone inscribed: Terribilis est Locus Iste – “This Place Is Terrible”; inside, a grotesque figure of the devil in a green robe bears the holy water.

Some believe that the irreligious symbols contained hidden codes either to “treasure” or to damaging documents that Sauniere used to blackmail the Vatican. He took the secret of his fortune to his grave in 1917, aged 65, but the mystery has endured.

“At the height of the madness in the 1970s, and it was complete madness, people were using explosives to blow holes all over the place,” said Mr. L’Huilier. “They got into the sewers, dug into burial areas, and smashed through stone walls. It had calmed down a bit. Then the book came out and put Rennes-le-Chateau back on the map again.

“Just two months ago someone pushed over a skull-and-crossbones keystone at the entrance to the cemetery. Luckily it wasn’t broken.”

Although many villagers believe that there was no need to move the priest’s body, at the request of his descendants it has been reburied in the grounds of the museum that adjoins the church.

“He’s lying at peace at last under a 3.5 ton sarcophagus surrounded by 5cubic meters of concrete. It’ll take one hell of a lot of explosive to get through that,” said Mr. L’Huilier.

While the grave robbers are unwelcome, tourism as a whole is a boon for the tiny, 152-strong community. Last year, the number of visitors surged by 50% to 120,000. Even on grey, rainy days, visitors keep coming up the winding road leading to the village. Last week, Amanda Zizzi-Knight, 48, who comes from Bath but now lives in Spain, said that she and her husband, Richard, 46, wanted to come after reading “The Da Vinci Code” and noticing similarities between the plot and local myth.

“It’s a shame that some visitors are causing problems, but it seems extraordinary that they’ve exhumed the priest and buried him somewhere else,” she said. “Still, there are a lot of strange people about.”

Marie-Laure Busquet, the head of the tourist office, said: “Lots of people are coming here because of ‘The Da Vinci Code.’ I don’t have a problem with them or the book – just the interpretation some put on it, and the damage they do. Some don’t seem to realize that it’s just a story.”