LAS VEGAS -- Two-time junior middleweight champion Fernando Vargas is disputing claims by the Nevada Athletic Commission on Friday that he used steroids before his loss to Oscar De La Hoya two weeks ago.

Marc Ratner, the athletic commission's executive director, said that Vargas' post-fight urinalysis came back positive for stanozolol. It's the same drug that cost sprinter Ben Johnson his gold medal and world record in the 100 meters at the 1988 Olympics.

Vargas, who was stopped by De La Hoya in the 11th round, said he was upset with the test results and wrote a two-page letter to Ratner defending himself.

"I did not knowingly take any prohibited substance, much less a steroid,'' Vargas wrote.

Vargas said he had taken nutritional supplements before the bout.

"I took what I was given and did not think to question, because I relied upon and trusted those around me,'' he said. "I know that steroids were banned and that there would be testing. The others responsible in my camp knew the same. I am upset beyond words that a positive test has been received.''

Vargas asked that a second sample be tested to eliminate any chance of laboratory error.

"This is a very sad situation for me,'' Vargas wrote. "I trained hard and the bout was a big one for me. While I lost, I thought I lost with honor. Now someone's stupidity threatens to take even that away from me.''

After the commission files a formal complaint next week, Vargas will have 30 days to formally respond. A hearing will be scheduled to determine a punishment. Ratner would not speculate on what type of punishment Vargas could receive.

"We'll all look him in the eye and say, `Why? What happened?''' commission chairman Luther Mack said.

Mack was upset about Vargas' results, especially since the commission warned boxing promoters on July 1 that fighters would be tested for steroids.

"It was a big fight. It was a great matchup pound for pound, a good fight for Nevada, good fight for the fans, and all of a sudden when the fight's over, we have this happen to us,'' Mack said. "That really bothers me.''