China of security

The Olympic doping tests are divided into three phases of sample collection, lab tests and publication of results. The testing period began on July 27 when the athletes' village opened, and would run until the end of the Games.

"We have strict regulations and standards in accordance with IOC rules, and we have been improving our work to form a rigorous chain of security," Games anti-doping chief Chen Zhiyu said.

In Beijing, the top five in the events and two randomly-selected athletes will be tested for banned substances like steroids and blood-boosters.

At least one IOC medical representative, a WADA (World Anti-Doping Agency) observer and a representative of the sports federations are present at each center when the athletes are tested.

At each center, urine samples are placed in two different containers. Once sealed, they can only be opened in the lab, so chances of swapping the samples will be minimized, said Chen.

Mirrors are placed on bathroom walls and those tested will be asked to roll up their sleeves to prevent cheats, he added.

All collected specimen are marked, put into suitcases and taken by guarded vehicles to the laboratory near the Olympic venues. The whole process is closely watched.

"People might want to break the rules, but we will make sure they are caught and punished," Chen said.

"We also try not to make the athletes feel overburdened by the tests," he added. "Athletes whose events are scheduled late in the day are allowed to be tested back in the village, rather than in the competition venues, so that they can directly go back to rest."

John Fahey, the WADA president, acknowledged the enormous and sound efforts made by China to host clean Games.

"They have the resources and a world-class laboratory. I have little doubt that they will make real efforts as they had in recent months in the preparation," said Fahey, according to a video clip on the WADA website.