A total of 133 people suspected of being involved in the prostitution business at a nightclub in Zhengzhou, capital of Henan province, have been transferred to prosecutors, China Daily learned on Tuesday.

Zhang Xiaolei, a Henan provincial public security department official, said police in the province broke up a large criminal gang after five months of investigation, searches and forensic work.

On Nov 1, about 1,000 police raided the Royal No 1 Nightclub, which was found to have been engaged in the sex trade since it opened in August 2012, Zhang said.

Eight city police officers are under investigation on suspicion of protecting the prostitution business at the nightclub, the Zhengzhou discipline inspection and supervision department said on Friday.

They include Zhou Tingxin, deputy director of the city’s public security bureau.

Wang Jie (not his real name), who used to be the nightclub’s marketing manager, said the price of rooms at the club ranged from 990 yuan ($160) to 9,900 yuan, and customers’ average nightly bill was more than 5,000 yuan.

Liu Fei (not his real name), former public relations manager at the club, said the business had more than 1,000 prostitutes when the nightclub opened, and the number later fell to 500.

"The minimum income of the prostitutes was more than 100,000 yuan per month,” Liu said.

Information that police gained from the reception desk computer showed that the club brought in more than 200 million yuan.

The club was in a six-story building with 150 rooms, and the largest could hold about 100 people. The Royal No 1 used to be considered the best place for entertaining clients and bribing officials in the city, former customers said.

"I spent about 2 million yuan in the nightclub to entertain my clients and officials,” said Qi Guang (not his real name), a businessman engaged in investment guarantees.

Qi said that he had to do so to develop his business and earn more.

According to provincial police sources, 256 suspects were arrested, with 133 sent to prosecutors and the rest detained or fined.

A further investigation is underway, and police are searching for additional suspects, Zhang said.

Prostitution is illegal in China. However, it is often offered in nightclubs and other entertainment venues as well as hotels. A major crackdown, in which more than 500 suspects were caught and 73 gangs busted across the country, came hours after media reports in February revealed that hotels in Dongguan, Guangdong province, were offering sex services.

Contact the writers at qixin@chinadaily.com.cn and malie@chinadaily.com.cn.