The biggest Chinese airline said Thursday its chairman is being investigated by the country’s anti-corruption agency.

China Southern Airlines said Si Xianmin is being investigated “by the relevant authorities for suspected serious disciplinary violations.” The phrase usually refers to corruption.

No details were given in the brief statement to Hong Kong’s stock exchange. The statement followed a similar announcement posted late Wednesday on the website of the Central Commission for Discipline Inspection, China’s top anti-graft body.

Si, who has been chairman since 2009, is the latest top executive at a state owned company caught up in President Xi Jinping’s widening anti-corruption crackdown.

Earlier this week, the commission said it was investigating the general manager of Dongfeng Motor, China’s second-largest automaker.

China Southern is the country’s biggest airline by passengers and fleet size. The company, which is based in the southern boomtown of Guangzhou, is one of three state-owned carriers that dominate the country’s fast-growing aviation market.

China Southern and Dongfeng Motor were among 13 state-owned companies targeted a year ago in a round of inspections by the anti-corruption watchdog.

The airline said last month that an executive vice-president was placed under investigation for suspected bribery.

Photo Credit: Iain Gray, left, managing director of Airbus UK, and Si Xinmin, chairman of China Southern Airlines, shake hands as they agree a purchase agreement for ten Airbus 330's, during the EU/China summit in the Great Hall of the People in Beijing, China. China Southern Airlines said Thursday, Nov. 5, 2015 that Si Xianmin is being investigated "by the relevant authorities for suspected serious disciplinary violations." The phrase usually refers to corruption. (AP Photo/) Kirsty Wigglesworth / Associated Press