Anti-Mafia prosecutors said Tuesday they are investigating a reported Mafia death threat against the Italian author of "Gomorra," the best-selling expose on the criminal underworld in Naples.

Naples-based prosecutor Franco Roberti said that his unit is looking into an informant's claim that the Camorra crime syndicate is planning to kill journalist Roberto Saviano by December.

"We are investigating to verify how true the claim is," Roberti said by telephone.

The prosecutor said the reported threat involved an attack along a highway, which also would target Saviano's police escort.

Saviano has been under police protection since 2006 when his book "Gomorra," denouncing the Camorra's hold on everything from garment industry to drug running to waste disposal, became a best-seller in Italy.

The writer could not be reached for comment Tuesday.

In the book, which has been published worldwide and was released in the United States last year, Saviano said Camorra-run companies routinely win contracts to dispose of toxic waste from northern Italian industries by underbidding competitors, then dispose of it illegally and untreated in the region's rivers and dumps.

The book was the basis for a film of the same name, which won second place at the Cannes Film Festival this spring and is Italy's hope for best foreign-language film at next year's Academy Awards.