Most of the athletes competing at the winter Olympics will be tested at least once for doping, the International Olympic Committee said Sunday.

Confirming its anti-doping plans at the Vancouver Games, the IOC's executive board said drug tests would be conducted on the top  five finishers in each event, plus two others selected at random.

"The vast majority of the approximately 2,500 athletes who are coming to Vancouver will be tested at least once before the Games end on 28 February," a statement said.

That could be almost double the 1,200 athletes who were tested at the 2006 winter Games in Turin.

Meanwhile the board has opened an investigation into a doping case involving a winning US relay team at the 2004 summer Games in Athens.

IOC vice-president Thomas Bach said he would lead a three-man panel into the case of Crystal Cox, who ran in the preliminaries of  the winning 4x400m team.

Cox has admitted to using anabolic steroids and accepted a four-year suspension and disqualification of her results from 2001 to 2004, the US Anti-Doping Agency said last month.

Bach said he did not wish to speculate on the outcome of the investigation.

"We will give her the opportunity one way or the other to be heard, but first of all we have to check the documents to see how far the admission reaches and then we can take it forward," Bach said.

The US team of Sanya Richards, Dee Dee Trotter, Monique Henderson and Monique Hennegan won the Athens 4x400m relay final ahead of Russia and Jamaica.

Following the Marion Jones doping case, the IOC stripped the US of its gold medal in the 4x400m relay and bronze in the 4x100m relay won at the 2000 Games.

The US men's 4x400m relay team was also stripped of its Sydney gold after a doping admission by Antonio Pettigrew.

On-site drug testing has started in Vancouver with the opening of the Olympic Village on 4 February. More than 800 athletes will be tested before their competition, the IOC said.

IOC president Jacques Rogge had already pledged a zero-tolerance  policy on doping at the Games. Anti-doping measures are to include storage of samples for retests once test methods for new substances  have been developed.

Canada has spent almost 16 million US dollars on a new testing lab with state-of-the-art equipment next door to the Olympic speed skating venue in Richmond.

The Turin Games saw only one positive case in Russian biathlete Olga Pyleva, but also an unprecedented Italian police raid on the quarters of the Austrian cross-country ski and biathlon team and the eventual banning of six athletes for life.

In another development, former Samsung chairman Lee Kun Hee, who  was indicted in 2008 in a financial and tax evasion case, was reinstated as a member of the IOC.

It follows a decision last year by the South Korean government to pardon Lee.

However the IOC's executive board agreed with the ethics commission recommendation that Lee be reprimanded and suspended from the right to sit on any IOC commission for five years.

The commission said Lee had "violated the ethical principles set  out in the Olympic charter and the IOC code of ethics" and "has tarnished the reputastion of the Olympic movement."

Lee was given a three-year prison sentence suspended for five years in July 2008 after being convicted of the charges before being pardoned in December 2009.

Lee's reinstatement will be seen as a boost for Pyeongchang's bid to host the winter Olympics in 2018. The South Korean venue is bdding against Munich and the French resort of Annecy.

--Sapa--