JINAN, March 2 (Xinhua) -- Chinese police have arrested two more men in a nationwide crackdown on the distribution of sexually explicit photos featuring Hong Kong entertainer Edison Chen, police in east China's Shandong Province said on Sunday.

Hong Kong police have been hunting for the first releaser of the photos and had made several arrests.

At least 13 people have been arrested on the Chinese mainland in connection with the photos. Chinese law prohibits the production, duplication, selling or circulation of pornographic products even without the purpose of making profit. Offenders can face detention of up to 15 days.

Ten people who allegedly produced, sold or bought computer discs of the photos were arrested in the southern city of Shenzhen in February, when police confiscated about 250 discs and six computers used to produce the discs.

An 11th person, surnamed Yu, was detained for 10 days in Zhoushan City, Zhejiang Province, on Feb. 22. He was found to have downloaded 260 photos on his computer and uploaded the photos to the album of his QQ space to attract other Internet users.

On Saturday, police in the central China province of Hunan sentenced two men to five days detention for disseminating the explicit photos on the Internet.

Last month, the Chinese Internet search engine Baidu.com was asked by a Beijing Internet self-discipline organization to make a public apology for allowing the circulation of the photos.

A 25-year-old man surnamed Wei was arrested on Feb. 12 for allegedly uploading 1,174 shots featuring Chen with female celebrities on to a chat room of the instant messenger QQ.com for downloads, according to the Internet supervision police brigade in Zibo City.

Wei allegedly provided links to the chat room at cbbn.bbs, a popular on-line forum, to canvas interest. Wei was detained and is awaiting trial.

The Zibo police said Wei confessed that he obtained the photos from another person outside Shandong when the pictures started to leak out.

The other man, surnamed Li, was given a ten-day detention and fined 3,000 yuan (420 U.S. dollars) on Feb. 15 for uploading more than 180 copies of the photos to his personal space at QQ.com.

Police in Tai'an, in Shandong, said Li, 21, provided links and codes to access the photos through his web page to solicit visits to increase its popularity.

The photos, reportedly copied by a computer repair shop assistant from a faulty laptop believed to belong to Chen, began to appear on the Internet from Jan. 27.

On Feb. 21, Chen made a public apology and announced that he would quit the Hong Kong entertainment industry. He admitted most of the photos were taken by him. "These photos were very private and have not been shown to people and were never intended to be shown to anyone."