Chinese authorities have detained six former employees of Tencent as part of a bribery investigation, the Chinese internet giant said on its Weibo microblog site.

Patrick Liu Chunning, executive director of Alibaba Pictures, has been detained by authorities as part of a probe into allegedly taking bribes when he was with Tencent, Reuters reported. Liu had worked in Tencent’s online video business.

The news comes as Chinese President Xi Jinping in recent months has stepped up a nationwide crackdown on corruption by government officials as well as executives at private companies.

In April China Telecom’s former president and chief engineer, Leng Rongquan, was put under investigation for “suspicion of serious violations of the law” by the Central Commission for Discipline Inspection (CCDI). In February China Telecom and China Mobile were among 26 large state-owned companies targeted by the CCDI for inspection.

Shenzhen-based Tencent said on its official Weibo account: “We are extremely shocked by the news. We support Tencent’s anti-corruption efforts and believe Tencent was being objective and fair regarding its report to the police.”

Liu and other former members of Tencent’s video business left the company after a management reshuffle in 2013 and later joined Alibaba.

Tencent is one of the largest internet companies in the world and runs the country’s biggest messaging app — WeChat — and one of the largest web portals in China.