The Olympic Council of Asia (OCA) said on Wednesday that there was no evidence to prove collective doping by Uzbekistan after the country's two athletes were caught for using the same banned stimulant.

Wrestler Jakhongir Muminov tested positive for Methylhexaneamine in an out-of-competition screening on Nov. 19, the day when his compatriot Shokir Muminov was stripped of his silver medal in the games' first case.

The two Muminovs are not related.

Dr. Mani Jegathesan, chairman of OCA medical commission, said there was "no evidence to prove the systematic use of doping" by Uzbekistan.

"They are two separate doping cases," he said.

"We take each case separately, but because it involved the same country, and the same substance ... we have indicated to them that it would be worthwhile to investigate," Jegathesan said.

When asked about further sanctioning if collective use of doping is proven, the OCA medical chief said: "As far as the OCA is concerned, our job is completed."

He added any further sanctioning will rest with the international federations and national authorities.

So far, more than 30 Uzbek athletes have been tested, said Jegathesan.

Uzbekistan delegation officials refused to comment on the positive cases when contacted by Xinhua.

The 23-year-old Jakhongir Muminov is a Greco-Roman 84kg division wrestler who didn't win medal in Guangzhou.

"The athlete has been disqualified from these games and his performance in the competition has been nullified," said Jegathesan.

As of Nov. 23, the organizing committee had conducted 1,262 tests, among which 1,090 have returned the results, according to Jegathesan.

Shokir Muminov, 27, lost to South Korea's Kim Jae-Bum by ippon in the 81kg division final, while Japan's Masahiro Takamatsu and Islam Bozbayev of Kazakhstan shared third place.

Takamatsu and Bozbayev were raised to joint second and awarded silver medals last Saturday.

All samples collected at the Guangzhou Games are being tested at the WADA lab in Beijing, which conducted drug checks for the 2008 Summer Olympics.

Methylhexaneamine has been the subject of several high-profile doping cases since the WADA added the substance to its banned list this year.

Nigerian sprinter Osayomi Oludamola was stripped of her Commonwealth Games 100 meters gold medal for using Methylhexaneamine. Six Indian wrestlers and three swimmers also tested positive for the same drug ahead of the Games.

The substance is widely used as a nasal decongestant but is also found in recreational drugs. A component of flower oil, the substance is a common ingredient in a variety of nutritional supplements and easily available on the Internet.

Some athletes have said they unwittingly ingested Methylhexaneamine when using supplements or other products.

"This drug is new," said Zhao Jian, deputy director of China Anti-Doping Agency. "Stimulants are being used in the world more than any other categories of doping."

In last Asian Games in Doha, four weightlifters, including two Uzbekistan athletes, were disqualified for positive doping tests.

(Xinhua News Agency November 24, 2010)