Kevin Chen, secretary general of Taiwan's Olympic Committee, said samples taken from Kuo, as well as two other members of the baseball team, Yeh Chun-chang and Lin Yi-chuan, tested positive for banned drugs before the December competition.
The three players said they had taken either cold or pain medications containing a banned substance, Chen said.
All three competed at Doha but received verbal warnings and were asked to clear their medications with the team doctor, Chen said.
"The situation is quite innocent," Chen said in a phone interview.
Taiwan beat Japan 8-7 in the gold-medal game at Doha.
Kuo, a left-hander, did not pitch in the final, and Taiwan's manager said at the time he didn't feel well.
The murky circumstances of Kuo's absence prompted an investigation by the newspaper China Times, which reported Kuo's positive drug test Monday.
China Times said Kuo didn't pitch against Japan because he had taken pain medication and that his pitching wasn't in good shape.
Chen said three other people in Taiwan's 391-member Asian Games delegation also tested positive for banned substances, but the results were also the result of taking cold or pain medication.
"I never had a problem before, so I don't know how it came to this," Kuo said.
Patrick Courtney, Major League Baseball vice president of public relations, said the Commissioner's office will look into the matter to see if disclinary action should be taken.
Kuo said he was more concerned about preparing for the upcoming season, as he remains in the mix for the fifth spot in the Dodgers starting rotation.
"It's already passed," Kuo said of the December incident.
Copyright 2007 The Associated Press. This story was not subject to the approval of Major League Baseball or its clubs.