Serie A club Napoli came under scrutiny on Wednesday after the country's Finance Police raided the club in relation to suspicions of financial foul play, media reports said.
According to the domestic ANSA news agency, police, who took away a number of documents from the club, were acting on a mandate from the public prosecutor in Naples.
The raid was carried out by Italy's Guardia di Finanza, a wing of the armed forces which deals with financial crime and smuggling and comes under the auspices of the Ministry of Economy and Finance.
Reports said the documents seized are in relation to an investigation into the purchase and sale of rights on the performances of team players, the relationship with player agents and any related financial movements.
Napoli, whose president is former film-maker Aurelio De Laurentiis, played down the search through their lawyer Mattia Grassani.
"It's a case of gathering information and obtaining documents, but nobody is being investigated and there are no accusations," said Grassani.
"Since the beginning of president De Laurentiis's tenure the contracts at Napoli have been drawn up rigourously and conform to the laws governing tax."
Police also carried out searches at the offices of the Italian football federation (FIGC) in Rome.
A FIGC spokesman said: "The police requested copies of contracts between agents, the players and the club and we obliged. That is all we can say on the matter."
Reigning Italian Cup champions Napoli have been one of the top teams in Italy's Serie A so far this season and currently sit joint top with champions Juventus.
Along with Juventus, Napoli are the only other team unbeaten team in the league after six games. They are also involved in the Europa League and face PSV in Eindhoven on Thursday.
"The police requested copies of contracts between agents, the players and the club and we obliged. That is all we can say on the matter"
Italian football federation spokesman
The police raids are the latest in Italian football, which has been dogged in recent years by claims of match-fixing and illegal betting that have led to clubs being docked points or demoted with players and managers banned from the sport.
On Wednesday former Bari footballer Andrea Masiello and two associates were given suspended prison terms by a Bari court for their role in fixing several Serie A matches.
Masiello hit the headlines at the end of the 2011 season when it was revealed he had accepted cash to deflect the ball into his own net in a derby against Lecce.
Bari had already been virtually relegated but the goal secured victory, and Serie A survival, for Lecce.
The investigating magistrate, Michele Parisi, said four matches - Palermo v Bari, Bari v Sampdoria, Bari v Lecce and Bologna v Bari - were concerned by the investigation.
Earlier this year, police raided the training camp of the Italy national side just before the European championships as part of a country-wide probe into illegal betting on matches.
The coach of Serie A champions Juventus, Antonio Conte, was in August handed a 10-month touchline ban, recently extended to international matches, for failing to disclose knowledge of rigged matches during his time at Siena in the 2010-11 season.
Conte, the most high-profile casualty of the so-called "calcioscommesse" (football betting) scandal that involved dozens of players and clubs, is currently appealing the ban.