State-owned China National Petroleum Corporation (CNPC), one of the country’s largest oil and gas enterprises, has found its fourth executive in trouble this year.

Ma Wenjun, 59, former Communist Party committee secretary and director of the business department of a CNPC subsidiary in Guangdong, is now under investigation for suspicion of “violation of the law and discipline” — a phrase that usually means corruption — according to a statement Wednesday from the discipline inspection commission of northeast China’s Heilongjiang province.

Ma was appointed to work in Guangdong in January, after spending almost 20 years in CNPC petrochemical subsidiaries in China’s Xinjiang Uygur autonomous region. There, Ma had work connections with Hu Yongqing, former deputy manager at CNPC’s planning department who was put under investigation for similar reasons in February. 

CNPC is the parent company of listed arm PetroChina.

The other two CNPC executives put under investigation this year are Qu Guangxue, a senior executive in charge of political education, and Li Xinhua, a retired CNPC deputy manager.

Related: Shaanxi Anti-Corruption Official Under Investigation — for Corruption