Naples, September 17 - Police north of Naples responded to a tip to dig up suspected toxic waste in the Camorra mafia's heartland on Tuesday. Digging is expected to last throughout the week, with ongoing testing for toxic substances at the site in Casal di Principe, the hometown of the Camorra's infamous Casalesi gang. The Casalesis' wrongdoing, which has long included illegal waste-disposal, was exposed in great detail in Roberto Saviano's best-selling 2007 book Gomorrah, later turned into an award-winning film. Saviano has since lived under around-the-clock police protection after death threats. Tuesday's tip reportedly came from an unidentified State's witness with mafia links. So far the dig has reached a depth of six meters. Digging is planned to stop after 12 meters.