Chang Xiaobing, China Telecom’s chairman and CEO, resigned last week after being detained on suspicion of “severe disciplinary violations”, according to a statement by the Central Commission for Discipline Inspection.

The agency uses the term as a euphemism for corruption.

Chang took the helm at China Telecom in August, when the country’s second and third largest operators swapped chairmen. Wang Xiaochu, then chairman of China Telecom, was named head of China Unicom.

Sources said the investigation stems from activity during Chang’s more than ten years as head of China Unicom, South China Morning Post reported.

Chinese President Xi Jinping has overseen a wave of investigations targeting corrupt officials at state-owned firms over the past three years, with dozens of senior executives detained.

China Telecom said in a statement that its executive director, president and COO, Yang Jie, was appointed interim chairman and CEO until the board finds a replacement.