The performance of China's athletes in last month's Asian Games seemed too good to be true.

Reports today quoting Games officials said some of them probably were.According to Japanese media reports, organizing commission officials said banned substances have been detected in the urine samples of 11 Chinese athletes who participated at the Games, Asia's version of the Olympics.

The officials, who were not identified, reportedly said the samples indicated the athletes had abnormally high levels of testosterone or other performance-enhancing substances in their systems.

The names of the athletes were not released pending official confirmation, the reports said.

But Kyodo News Service, quoting unidentified sources, said one was Lu Bin, who won four gold medals and set a world record in the women's 200-meter individual medley.

It said another was Yang Aihua, who already has been banned for two years by FINA, the international swimming federation. Yang, who won the women's 400 freestyle in the World Championships in September, tested positive for testosterone in surprise tests before the competition in Hiroshima.

Chinese women swimmers won 12 of the 16 golds at stake in the world meet and all 15 of their races in the Asian Games, contributing to China's overall haul of 137 golds in 337 events.

Kyodo also identified Xiong Guoming, a male swimmer who won four gold medals, and track athlete Han Qing, winner of the women's 400-meter hurdles, as being among the 11.

It said eight of the 11 were swimmers and the others competed in track, cycling and canoeing. Other press reports said six were swimmers.

Dr. Yoshio Kuroda, who supervised the final set of tests conducted in Tokyo on Saturday, confirmed that high testosterone levels were found in both A and B samples for some athletes. Kuroda refused to comment on who was tested, or give their nationality.

Asian Games organizers contacted by The Associated Press confirmed the head of their medical commission was in Tokyo in connection with the tests, but also refused to comment further.

A formal hearing of the Olympic Committee of Asia's medical committee, which Kuroda chairs, must be held before results of the tests can be made public. Such a meeting could come within the next week.

In the world swimming championships, though they did not name China, more than a dozen coaches lodged a formal complaint over doping in the sport and requested stricter tests. That led to the surprise testing just before the Asian Games began Oct. 2.

FINA officials said the results of those tests indicated possible drug use among several other Chinese women, but were inconclusive.

Though Chinese sports officials insist they oppose drug use among athletes and publicly threaten to deal harshly with offenders, Yang's case is not the first.

Five Chinese swimmers have failed doping tests over the past two years - equaling the total number of athletes from other countries that have tested positive in FINA tests over the past 22 years.

Yang is at least the 34th Chinese athlete to flunk a doping test since 1987. Chinese officials acknowledge 24 of their athletes tested positive last year alone.

Another top female athlete, discuss thrower Qu Qiaping, tested positive for anabolic steriods in an out-of-competition test Sept. 26.

Today's reports, if confirmed, would raise serious doubts about the effectiveness of testing in general.

Only one athlete - the captain of the Thai men's soccer team - was announced to have flunked a doping test during the Asian Games.