The Chinese Weightlifting Association said on Wednesday it was shocked by news that three Chinese lifters were among 15 who have failed retesting of their samples from the 2008 Beijing Olympics.

The association said in a statement it will cooperate with the International Weightlifting Federation in the investigation and reiterated its stance of zero tolerance for doping.

"If, after investigation, activities are found to have violated the rules, the association will not tolerate this, and severe punishment will be meted out," the association said.

Earlier on Wednesday, the federation said in a statement on its website that 15 weightlifters from six countries, including 11 medal winners at the 2008 Games, had failed retests of their samples.

"In line with the rules and regulations, the IWF imposed mandatory provisional suspensions upon the athletes, who remain provisionally suspended in view of potential anti-doping rule violations until their cases are closed," the federation said.

The weightlifters who tested positive include Chinese gold medalists Chen Xiexia, who won the women's 48 kg division in Beijing, Liu Chunhong, winner of the women's 69 kg, and Cao Lei, who won the women's 75 kg.

All three tested positive for GHRP-2, a type of hormone that can increase endurance. Liu also tested positive for sibutramine, a stimulant.

The three could be stripped of their gold medals if the results are confirmed, The Associated Press reported.

Chinese weightlifters have not previously tested positive at the Olympics, and all of the Chinese lifters involved have retired.

Besides Chinese athletes, weightlifters from Russia, Ukraine, Belarus, Azerbaijan and Kazakhstan tested positive in the reanalysis.

After decisions taken by the International Olympic Committee, the federation took over results management of the cases.

The federation would not comment further on the cases until they were concluded, the statement said.

China's General Administration of Sport had not commented on the report by press time on Wednesday.

Chinese weightlifters won five gold medals at the Rio Olympics, which ended on Sunday.