Yesterday, Dr. Lawrence Rink told The Associated Press that there had been positive drug tests, but would not elaborate on how many athletes or identify them, saying the process would have to be completed with provision for possible appeals.

But Rink told a news conference today that "to date, we have absolutely completed 276 tests and I am happy to report that all tests to date are negative."

"Now, for my opinion I understand that because the process is so technical, there may be some misunderstanding but again I repeat that there is no positive test. There is clearly no scandal," Rink said.

"The laboratory process is a very detailed process and very specific and critical process ... the laboratory we are using here is recognized as one of the best in the world."

He said organizers expect to conduct more than 600 tests up to the final events Saturday.

"It's only after the appeal process, which can take up to one week to three months — in some instances if there is a court involved, it might take longer — can we then truly be sure if it's a positive test."

Earlier today, Rink retracted his earlier statement in a telephone call to The Associated Press, saying that he would announce at the later media conference that there were no "confirmed" positive tests.

"The final results were negative," he told The AP ahead of the news conference. "There could have been fault positives earlier and in those questionable cases, we do more sensitive tests. The fact is at the end they were all negative tests. I should not have said anything at all."

At the media conference, Rink said the details of the cases could only be made public after the whole process is complete.