Olympic chiefs are to investigate a major drug scandal in cycling after a rider took part in this year's Tour de France despite having tested positive for banned drugs several times before the race. The International Olympic Committee (IOC) said it was unhappy that its Paris drug-testing laboratory had not informed the IOC of the positive tests on the rider, who was also caught cheating with drugs during the Tour.

IOC medical officials did not name the rider, but said there had been only one doping case during the Tour, the most prestigious race in the sport.

Uzbekistan's Djamolidine Abdoujaparov was expelled from the Tour after he failed a drug test at the end of the second stage.

"We have to put the house in order in this matter," the IOC's medical chief Prince Alexandre de Merode said. "We are going to investigate. Positive tests (in our laboratories) have to be reported to the IOC."

IOC medical officials said the rider had produced positive tests four times before the Tour for the banned substances clenbuterol and bromantan.

The cases were reported to the cycling federations and the French sporting authorities, but not to the IOC which should be informed of all positive tests, they said.

Bromantan, a stimulant-cum-masking agent, has a controversial history, but it has been on the IOC's banned list of substances since February 1st, the officials said.