ZHENGZHOU - Eight police officers in central China's Henan Province are being investigated over suspicions that they harbored the prostitution business of a local nightclub.

Zhou Tingxin, former deputy chief of the public security bureau of the provincial capital of Zhengzhou, and seven other police officers were placed under investigation on April 18, after the Royal No. 1 nightclub was found to have been engaged in the sex trade since its opening in August 2012, an official with the disciplinary inspection department of the city said on Monday.

Police raided the nightclub on Nov. 1, 2013 after five months' investigation, transferring 133 suspects for public prosecution and subsequently closing the venue.

Prostitution is illegal in China. However, many nightclubs and other entertainment venues or hotels offer prostitution. A large-scale crackdown, in which over 500 suspects were captured and 73 gangs busted across the country, came hours after media reports in February revealed that hotels in the southern city of Dongguan were offering sex services.