Italian Prime Minister Silvio Berlusconi is being investigated in a case involving the alleged abuse of power and possible links to underage prostitution.
Officials in Milan say a summons has been issued to Mr Berlusconi and his lawyers, inviting him to talk to investigators.
The prime minister is suspected of abusing his power by having a teenage Moroccan nightclub dancer, whose stage name is Ruby, released from a police cell.
Mr Berlusconi denies any wrongdoing.
The case came to light last November, and prosecutors at the time questioned Milan police over Mr Berlusconi's involvement, the BBC reports.
The prime minister's lawyers say the investigation is absurd and groundless, and a serious interference in his private life.
News of the investigation came a day after a constitutional court ruled that a law that gave Mr Berlusconi immunity from prosecution was partially invalid.