(Guangzhou) – An investigation into a vice governor of the Guangdong Province is related to backing he gave to the sex industry in a town that became notorious for its brothels, several people with knowledge of the matter say.

The Communist Party's anti-graft watchdog said on February 4 it is investigating Liu Zhigeng for "suspected serious violations of discipline," the party's pet phrase for corruption.

The inquiry into Liu, the vice governor in charge of transportation and work safety supervision, is linked to his time as party secretary of Dongguan from 2006 to 2011 when he allegedly protected the rampant sex industry in the southern city, the sources familiar with his situation said.

Liu, who became vice governor of the province in 2011, was detained by police on the afternoon of February 4, they added.

Dongguan has for years been notorious for its thriving sex industry. It was common knowledge the manufacturing city's karaoke bars and barber shops were often fronts for sex workers and that brothels were easily found. In 2014, the state broadcaster CCTV aired news reports on Dongguan's vice dens, prompting a crackdown.

Liu was last seen in public on February 3 while overseeing the operations of the train station in Shaoguan, a city in the northern part of Guangdong, which was busy handling millions of migrant workers heading home for Spring Festival, the holiday many know as Chinese New Year.

Liu was born in Xingning, Guangdong, in 1956. His biography on the provincial government's website shows that he started his career as an elementary school teacher in 1973.

Six years later, he went to Jilin University, in the northeast, to study economics. Liu held various positions in the governments of Shenzhen and Dongguan before becoming vice governor.

Liu is the third top official in Guangdong to come under scrutiny since Xi Jinping launched a crackdown on graft shortly after becoming party boss in late 2012.

Wan Qingliang, the former party secretary of Guangzhou, tumbled in June 2014 and was later charged with taking bribes worth of 11.25 million yuan. An inquiry into Zhu Mingguo, the former chairman of Guangdong's political advisory body, started in November 2014.

The broad anti-corruption campaign has netted high officials in every province and figures in many fields, from state-owned enterprises to the military, but experts warn its effects will be short-lived unless changes are made to China is governed.

Chen Guangzhong, a professor of China University of Political Science and Law in Beijing, recently said that flaws in the political system, such as a lack of a system of checks and balances, must be fixed to prevent more dirty officials from emerging.

(Rewritten by Chen Na)