Police said Friday that they have booked nine people in an unfolding probe into the suicide of an actress amid allegations she was forced to provide sexual favors by her former agent.

Jang Ja-yeon, the 30-year-old actress, hanged herself at her house in Bundang, south of Seoul, on March 7. The case snowballed a few days later when her agent disclosed a seven-page suicide note, supposedly written by Jang, which said that a former agent had forced her to provide sexual and other favors to several high-powered entertainment figures and journalists.

Jang's suicide shocked many as the young actress had just begun to win fame from her supporting role in KBS TV's popular drama "Boys Over Flowers." Following her death, an anonymously-written list of names, later dubbed the "Jang Ja-yeon List," circulated over the Internet that included industry heavyweights to whom Jang was allegedly forced to provide favors.

In a press briefing on the progress of the investigation, Bundang Police Station in Seongnam, Gyeonggi Province, said that they have so far booked three entertainment agency officials, two directors, three financial industry officials and a private entrepreneur on charges of defamation, coercion and assault.

Included are Yoo Jang-ho, Jang's most-recent agent who disclosed the letter, on charges of libel for making the letter public through the media. Police are also trying to track down the head of Jang's agency, the former agent, accused of coercing the actress into offering sexual favors.

A court has issued an arrest warrant for the head of the agency, identified only by his family name Kim, who is now in Japan. Police officials have requested that Japanese authorities extradite Kim, as he has repeatedly defied summons by investigators.

The police decided to suspend interrogating five suspects until Kim is extradited, as they have had difficulty confirming the allegations without questioning him.

Criticism has mounted that police have done little to uncover the truth during the month-long investigation. Critics claim that investigators have not been active in questioning big names in the media and corporations allegedly mentioned in the suicide note and the circulated list.

Police decided to conclude their investigation into 11 directors, media-industry and financial-sector officials, which include journalists at broadcaster KBS that initially reported the existence of the suicide letter.