A leading US newspaper says China's former foreign minister was ousted because of an extramarital affair he had while serving as ambassador to the United States.
The Wall Street Journal also reported on Tuesday that Qin Gang fathered a child with the woman, who has not been identified.
Beijing announced in July that Qin had been replaced as foreign minister by his predecessor, Wang Yi.
The paper quoted sources as saying that senior Chinese officials were informed in August that Qin had been replaced as the result of an internal Communist Party investigation that uncovered "lifestyle issues." The phrase is usually used by the party to refer to sexual misconduct.
The probe is reportedly now focused on whether there was an adverse impact on China's national security.
A child born in the United States is automatically a US citizen. The paper quoted sources as saying the existence of the child with the US citizenship was part of the reason for Qin's dismissal, as it could harm China's national interests.
Asked about the report in a press conference on Tuesday, Chinese foreign ministry spokesperson Mao Ning said Beijing had already released information on the appointment and removal of the foreign minister, and she was not aware of any other information.
There is also growing speculation that Defense Minister Li Shangfu is under investigation over allegations of corruption. Li has not been seen in public for three weeks.