BEIJING — Lyudmila Blonska of Ukraine is under investigation for a positive doping test and could be stripped of her silver medal in the Olympic heptathlon.

The International Olympic Committee said Wednesday it has opened a disciplinary procedure into Blonska, who finished second behind fellow Ukrainian Nataliia Dobrynska last Saturday.

The IOC disciplinary commission and executive board are expected to rule on the case Thursday.

Lamine Diack, president of the International Association of Athletics Federations, said he had been notified of the positive result by IOC medical director Patrick Schamasch.

"Yes, I've just been informed," he said. "Only on my way here, Schamasch phoned me to say this athlete tested positive. The process is under way."

If found guilty of a doping offense, the 30-year-old Blonska would lose her medal and be expelled from the games.

Blonska is also competing in the long jump and was third in qualifying ahead of Friday's final. Her place in that event is now in jeopardy.

The third-place finisher in the heptathlon was American Hyleas Fountain, who would be bumped up to the silver if Blonska is disqualified. Russia's Tatiana Chernova would move up from fourth to the bronze.

Blonska served a doping suspension between 2003-05. If found guilty of a second offense, she could face a lifetime ban.

Blonska won the silver medal in the heptathlon at last year's world championships in Osaka, Japan, and took gold in the pentathlon at the 2006 world indoors in Moscow.

British athlete Kelly Sotherton, who finished fifth in the Olympic heptathlon, complained publicly for months that Blonska shouldn't be allowed to compete in Beijing because of her doping past.

"I'm pleased her teammate beat her," Sotherton said last Saturday. "That makes it bittersweet. I'd have been really upset if she'd won gold. The penalty you should pay if you take drugs is not to compete at the Olympics."

Four athletes have been disqualified and kicked out of the games so far for positive drug tests — Greek hurdler Fani Halkia, North Korean shooter Kim Jong Su, Spanish cyclist Isabel Moreno and Vietnamese gymnast Thi Ngan Thuong Do.

Earlier Wednesday, IOC spokeswoman Giselle Davies said a total of 4,133 tests had been conducted so far, including more than 3,290 urine controls and 840 blood screenings.

By the end of the games Sunday, the IOC will have carried out between 4,500 to 5,000 drug tests in Beijing, up from 3,600 in Athens four years ago.

Davies said 39 athletes had been caught ahead of the games in testing by international sports federations and anti-doping organizations.

"The IOC was very clear in the lead-up we would work in concert with all the anti-doping bodies," she said. "We feel the deterrent effect plays a part in what we see here. The athletes know the IOC means business."

Because of the spate of high-profile doping scandals in recent years, there is intense media and public interest in the test results from marquee Olympic events, especially the men's 100 meters.

Davies said she didn't know whether all tests had come back clean from Saturday's final in which Jamaica's Usain Bolt won the gold medal in a world record time of 9.69 seconds.

Davies said she wasn't privy to results from specific tests or events, noting 300 to 350 samples are being analyzed each day.

Normally, it takes 24 hours for a negative test to be confirmed, 48 hours for positive tests for steroids, and 72 hours for positive results for the blood-booster EPO.