A secretary who opened the envelope was sent for tests for possible anthrax exposure at a local hospital, Il Giornale said on its website.
The whitish-grey powder inside the envelope was due to undergo laboratory analysis later on Monday, the paper said.
A letter sent with the powder contained death-threats against Berlusconi and Italy's president, Giorgio Napolitano, and was signed by the obscure 'People's Armed Defence Group', Il Giornale said.
A similar envelope also arrived on Monday at best-selling Italian daily Corriere della Sera in Milan.
Il Giornale is owned by Paolo Berlusconi, Silvio Berlusconi's brother.