Liu Shihua, a divorcee, and his partner Zhang Anfen, a mother of another teen, were both residents of Wangjiaqiao village in the province's Kunming city.

Zhang, 34, has reportedly been released on bail.

On March 16, a tip-off led the Wangjiaqiao police to raid Liu and Zhang's Wangjiaqiao home where they "found reasons to suspect" the duo was forcing Liu's teenage daughter into the flesh trade.

"Our patrol officers present at the scene saw one of the girls walk out of the house with a man surnamed Wang," police said. "We had information the girl was pimped to the man and were ordered to arrest the two."

Police said they did not know Liu had already become aware of their presence outside the house and "asked the two minors to exchange identities to fool the officers".

Liu, Zhang and Liu's friend Pu Enfu, who was present in the house, resisted arrest and "had to be subdued by force", police said.

The suspects were released the following day for lack of sufficient evidence.

On March 19, Pu, 44, obtained a forensic medical certificate from the Legal Medical Expert Hospital in Kunming, which stated he had "several fractured ribs and injured facial tissues".

Liu and Zhang, who also alleged "physical torture by the cops", did not undergo a forensic test saying it was "too expensive".

Liu, however, produced a medical certificate claiming his daughter was a "virgin", hence could not be a prostitute.

Days later, two patrol officers in the raid, Li Jiaquan, and Nie Zhenglu, were sacked, while the director of the Wangjiaqiao police, Nie Tianjie, was recorded for demerit. Wang Yunhui, the head of the team investigation the case, received a warning.

Liu and Zhang subsequently took the matter up with the Kunming public security bureau, demanding a minimum compensation of 16,000 yuan ($2,350) for "injuries sustained during police torture", local media reported.

The police offered the duo 15,000 yuan to settle the matter, but the two parties did not reach a settlement, newspaper reports said.

A Yunnan newspaper also reported on June 2 that the latest medical test on the two girls showed that one had an "integral hymen", while the other's was "worn out".

"In order to extract a large sum of money, Liu forged evidence to provide to the media," the statement said.

The public security bureau said it would work with local authorities to find Liu's daughter a "place to stay".

It also urged the local education bureau to help Zhang's daughter return to school.