Officers of the Guardia di Finanzia - the Italian police department which focuses on financial crime - spent more than two hours going through documents at Napoli's Castel Volturno headquarters at the request of the Neapolitan prosecutor's office.
A statement issued on Wednesday afternoon on sscnapoli.it read: "Today, the Guardia di Finanzia accessed the company offices to acquire information concerning a process initiated by prosecutors in 2007, of which the details are not known.
"We stress that the club, its representatives and its directors are not being investigated.
"The club, in keeping with a principle it has always followed, is on the side of the judiciary when it comes to ascertaining the truth of any matter."
It was also reported that police spent 30 minutes at the Rome headquarters of the Italian football federation (FIGC), looking through paperwork before taking away various documents.