After a writer made the claim that a lost panel of the “Ghent Alterpiece” was buried underneath the city, the mayor is urging citizens not to dig it up themselves.

After Adoration of the Mystic Lamb was completed by Hubert and Jan van Eyck in 1432, it was placed in the St Bavo Cathedral in the Belgian city of Ghent, where it’s been admired and deeply coveted as part of the Ghent Altarpiece. Napoleon stole it, it was nabbed and then returned in World War I, and in World War II, it was saved just before getting blown to bits by the SS. It’s always been recovered, except for once: In 1934, two of the 12 panels were stolen, and despite the 1 million Belgian Franc reward, one of the two lost panels was never returned.

On Friday, a author and engineer named Gino Marchal announced that he had solved the mystery of the remaining panel, claiming that it was buried under a square in Ghent’s central Kalandeberg area. Marchal’s theory stems from 13 puzzling notes that belonged to a stockbroker who died the year the panels were stolen, and announced on his deathbed that he knew the location of the lost masterpiece. The notes include the French words for bird, art, Jean, Nina, Erpe, and fur, and the number 152; Marchal believes he found four locations related to these “clues,” all 152 metres from the same point in Kalandeberg square.

While many have written off Marchal’s theory as a publicity stunt to gin up attention for a new book he’s releasing, Ghent mayor Daniel Termont is still warning the citizens not to go treasure hunting at the painting’s supposed hiding spot. “Do not undertake anything yourself. Please do not undertake anything yourself,” he warned twice in the Flemish newspaper De Standaard. “That is work for the police and the public prosecutor’s office.”