The world's second-largest retailer Carrefour, which operates 101 hypermarkets in the mainland, blew the whistle on alleged bribery in some of its mainland stores that left eight managers detained by police, according a mainland media report.

The French retailer said in an internal memo that it had recently probed its central merchandising unit and seven stores in Beijing for the alleged bribery, leading to 22 people including 12 suppliers being questioned by the Beijing police and eight managers detained for investigation, China Business said.

The detainees, many of whom were managers of seven stores in Beijing and fresh food merchandisers, allegedly accepted kickbacks from suppliers, it said. A spokesman for Carrefour's mainland operation declined to comment on the anti-graft investigation but admitted that the group had looked into some corrupt practices since the headquarters set up a risk management taskforce, the paper said.