Dr. Michael Riding, the IPC medical director, said the powerlifters from four countries had tested positive for performance-enhancing substances in out-of-competition tests conducted in Sydney before Wednesday's opening ceremony.
The athletes, whose names were not released, and their national committees had been informed of the positive results and the athletes withdrawn from competition pending the result of testing on their second sample, the B sample.
Riding said details would likely be revealed late Saturday, following doping hearings if the B samples confirmed the initial positive tests.
The athletes will be punished if backup tests are also positive, the IPC said.
"I am disappointed of course that we still have athletes who believe they need drugs to achieve their ultimate goal," IPC president Robert Steadward said.
"On the other hand I feel good we were able to do out-of-competition testing and prevent those athletes from competing and causing problems further down the line."
There were no positive drug tests announced at the 1996 Paralympics in Atlanta, he said.
Weightlifting was tarnished during the Sept. 15-Oct. 1 Sydney Olympics, where four lifters were among five athletes stripped of medals after testing positive for banned substances.
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