Regulators launched a probe into several jewelry enterprises for allegedly manipulating gold prices and monopolizing the Shanghai market, People.com.cn reported on Friday.

The enterprises, including Shanghai-listed Yuyuan Tourist Mart and Laomiao Gold, have been deciding a "benchmark price" for some jewelry enterprises in the city through the Shanghai Gold & Jewelry Trade Association, which has more than 30 gold jewelry enterprise members, the report said.

The gold price offered by members shall not fluctuate more than 3 percent over the "benchmark price", according to the association's rules.

The rule was terminated in 2011 due to its conflict with anti-monopoly legislation, but many jewelry enterprises still practice the "benchmark price" rule, People.com.cn report said.

The National Development and Reform Commission and Shanghai Municipal Development and Reform Commission are investigating the case, the report said.