China’s top banking regulator is set to complete an investigation into the relationship between Evergrande and a little-known Chinese regional bank, which could pose a new threat to the world’s most indebted property group and its billionaire founder Hui Ka Yan.

Chinese media reported in May that the China Banking and Insurance Regulatory Commission (CBIRC), the country’s top banking regulator, was examining more than Rmb100bn ($15.6bn) of transactions involving the Shenzhen-headquartered developer and Shengjing Bank, a Hong Kong-listed lender it part-owned. The probe is nearing its final stages, according to two people familiar with the matter.

The regulator scrutinised how the bank became exposed to Evergrande’s debts and Hui’s role in the corporate relationship, the people added. Chinese media has reported that the regulator has focused on transactions involving Evergrande and Shengjing, in which the developer owned a significant stake.