Chinese investigators have questioned at least two more officials at the nation’s insurance watchdog after starting a probe into the agency’s former top official Xiang Junbo, according to a person with knowledge of the matter.

The officials, including former China Insurance Regulatory Commission Chairman Xiang’s secretary Zhu Yanhui, who is also deputy head of the agency’s General Office, were interviewed after China’s anti-graft agency announced Xiang’s probe last month, the person said. The other official is He Hao, a deputy at the regulator’s property insurance department, the person said, declining to be named as the investigation is still ongoing.

The CIRC and the Central Commission for Discipline Inspection didn’t immediately reply to faxes seeking comment. Calls to the offices of Zhu and He went unanswered; He’s mobile phone was switched off and he didn’t immediately respond to a text message.

Chinese leaders are seeking to clean up and rein in risks in a sector that President Xi Jinping said is key to economic stability. Officials overseeing banking, insurance and securities have issued a flurry of directives as they seek to prevent the eruption of any systemic financial risks amid rising hazards in bond defaults, shadow banking and non-performing bank loans.

The probe into Xiang, the highest-ranking financial official to be investigated, came as regulators have increased their scrutiny of aggressive investments and sales of risky products by some insurance companies.

Earlier high-profile probes at China’s three financial regulators have included Yao Gang, former vice chairman of the China Securities Regulatory Commission, and Zhang Yujun, an assistant chairman at the securities watchdog, in 2015. The anti-graft commission said in February that People’s Insurance Co. (Group) of China Ltd. President Wang Yincheng was under investigation on suspicion of severe disciplinary violations.

While all those officials have been removed from their positions, the government doesn’t always reveal the results of its investigations. Probes do not necessarily lead to formal charges and sometimes people get released after brief detentions for questioning.