Guangzhou Communist Party leader Wan Qingliang is being investigated for corruption, a party disciplinary commission has said.
Wan Qingliang, 50, is suspected of “serious disciplinary violations”, a term generally used to indicate corruption.
He is regarded as the city’s top official, ranked above the mayor.
Tens of thousands of officials have been arrested since President Xi Jinping began an anti-corruption campaign in 2012.
Xi Jinping has warned that the party’s very survival is threatened by corruption and has vowed to root out every corrupt official, whether “tigers” or “flies”.
A central government audit recently uncovered 314 serious disciplinary violations, up from 175 serious cases revealed the year before.
Correspondents say that before the investigation Wan Qingliang had been seen as a rising star in the Communist Party, developing a reputation for frugality while serving as Guangzhou’s youngest ever mayor.
Guangzhou is China’s sixth largest city and capital of the economically significant Guangdong province, which borders Hong Kong.