Liu Chunhong during 2008 Beijing Olympic Games， file photo.

The Chinese Olympic Committee (COC) reiterated its zero tolerance to doping on Friday and vowed to investigate the cases involving three female Chinese weightlifters after the trio was stripped of gold medals won during 2008 Olympic Games by the world's top sports body.

The International Olympic Committee (IOC) announced on Thursday the disqualification of the three female Chinese Olympic weightlifting gold medalists Cao Lei (75 kilograms), Chen Xiexia (48 kilograms) and Liu Chunhong (69 kilograms) along with five other athletes who competed at 2008 and 2012 Summer Games.

"The COC condemns the three athletes who violated the spirit of sportsmanship and Olympics for doping," the COC said in a statement published on its official website on Friday.

"The COC respects the decisions made by the IOC and will investigate the cases with related bodies … We are in solidarity with the IOC to protect clean athletes and fight against doping."

The disqualified athletes should have the medal, the medalist pin and the diploma obtained in the respected discipline returned, the IOC said.

The three Olympic weightlifters, including Chen who won China's first gold medal at the 2008 home Games, all tested positive for prohibited substance GHRP-2 and metabolite (GHRP-2 M2) after re-analysis of their samples from Beijing 2008, the IOC said.

A Chinese anti-doping expert who requested anonymity told the Global Times that the drug taken by the athletes stimulates production of growth hormones and sibutramine, with the latter possibly serving as a masking agent.

"It is common knowledge among all athletes that these substances are prohibited. Unless they have an exemption for using the drugs … It's all illegal," he said.

The disqualification leaves China facing a ban on weightlifting from international competitions for a year.

Weightlifting's world governing body, the IWF, introduced the sanction in 2016, aiming to crack down on doping, which is rife in the sport. The IOC is keeping samples from past Games for up to 1o years, conducting retests as newer testing methods are developed in an effort to try to root out any cheats.

The re-analysis led by the IOC of the samples from the Beijing and London Games have so far caught more than 100 doping offenders.

Athletes in track and field and weightlifting might be more likely to be caught doping because the prohibited substances, which enhance the aerobic capacity of muscles, are most effective in improving the performance of athletes in such sports, the expert said.

Several Western media accused China of state-sponsored doping, but the Chinese anti-doping expert said they are just analyzing cases with "double standard."

"There are also many athletes from Western countries who were found using prohibited substances in recent years, but the global media usually tries to paint their indiscretions as personal mistakes," he said.

"However, when it comes to countries like China, the issue becomes 'nationally organized behavior.' To some degree, it is a double standard," he remarked.