On the eve of the world championships, track and field got the last thing it needed--another drug scandal.

Already reeling from a series of high-profile doping cases, the sport took a massive blow today with the news that one of its most prolific stars, sprinter Merlene Ottey, had tested positive for a banned steroid.

The 39-year-old Jamaican pulled out of the championships, which will open Saturday, after learning that traces of Nandrolone were found in her urine sample at a meet in Lucerne, Switzerland, on July 5.

Nandrolone, a performance-enhancer that goes back to the 1970s and has been detectable for years in conventional drug controls, has produced a recent rash of positive tests in track and field and other sports.

Experts said this could be the result of more sensitive testing procedures or a sign that Nandrolone is being ingested unwittingly in other products or food supplements.

Ottey, who has won more world championship medals (14) than any other athlete, said she was the victim of a "terrible mistake" and would fight to prove her innocence. She offered to undergo another test.

"To write this statement has been the most difficult and emotionally draining experience of my life," Ottey said in announcing her withdrawal. "I have lived my personal and athletic life with the utmost honesty and integrity.

"I have applied only the highest ethical standards to myself and expect the same from others. I have always proclaimed fairness in sports and adamantly oppose the use of banned substances."

The International Amateur Athletic Federation, the sport's world governing body, confirmed that Ottey's "A" sample turned up positive for Nandrolone. The backup "B" sample is due to be analyzed in the next few days at the IOC-accredited laboratory in Lausanne, Switzerland.

If the "B" sample is also positive, Ottey faces a possible two-year ban that would effectively end her career and erase her hopes of competing in her sixth Olympics next year in Sydney.

"It was a shock to me," said IAAF general secretary Istvan Gyulai, who was notified of the positive test this week. "It was also a personal disaster [for Ottey]. . . . You can say it is sad, it is disappointing, that at a rather mature age, some athletes believe this is the way to continue at center stage."

Ottey's agent, Daniel Zimmerman, said the sprinter was adamant that the test result was wrong.

"She is a strong personality that has given the sport something for the last 20 years and she does not want that taken away," he told BBC radio. "She will fight this; she will get the best help possible from all sides."

Since 1979, Ottey has been tested approximately 100 times and all results were negative, her management company FKG said. The most recent tests at Ljubjliana, May 12, and in Stockholm, July 30, also have shown negative results, the group said.

IAAF and Jamaican track officials said they were upset the news of the positive test had leaked out before the "B" sample test. Under confidentiality rules, an athlete is not supposed to be identified until both samples have been analyzed.

More than 10 years after Ben Johnson was stripped of his gold medal and world record at the 1988 Seoul Olympics, drugs are tarnishing the image of the sport like never before. In the last month alone, Cuban high jumper Javier Sotomayor, the world champion and world record holder, tested positive for cocaine at the Pan American Games and was stripped of his gold medal; 1992 Olympic and world 100-meter champion Linford Christie of Britain was suspended for a positive Nandrolone test; and U.S. 100-meter champion Dennis Mitchell received a two-year ban for testosterone.