News reports say one of China's most powerful politicians interfered in an investigation involving a family member before he was fired last week.
Bo Xilai's removal as Communist Party boss of Chongqing city marked China's highest-profile dismissal in years.
His sudden departure on Thursday followed a visit to the US consulate in the southwestern city of Chengdu by Chongqing's police chief, Wang Lijun, in what was believed to have been an attempt to seek political asylum.
The reports on numerous online news sites said Bo transferred Wang after the police chief informed him of an investigation into one of Bo's relatives.
Party spokesmen did not immediately respond to requests to verify the reports, carried on websites inside and outside China.