For what reason did the people of La Matosa race to the Witch's house with a variety of tools after her body was found?

Once people in town began to learn that the Witch's body had been found in the canal, more and more of them showed up at the Witch's house. They were there to search for the Witch's alleged treasure, so they brought implements like shovels, picks, and sledgehammers to help them in their search.