Former WBA Supermiddleweight champion Brian Magee has tested positive for Oxilofrine, the same substance found in Asafa Powell's system last week, and has been banned for six months.
The Lisburn native, who represented Ireland at the Atlanta Olympics in 1996, is the latest athlete to be caught using the banned substance.
Magee failed the doping test taken immediately after losing his world title to Mikel Kessler last December.
Magee said he feared his career was over when he was informed of the positive test in February. Having identified a supplement as a possible cause, he was handed a retrospective ban which is due to expire next week.
Magee said: "I was in total shock when I was told I had tested positive, and I honestly thought someone was playing a joke.
"All I could think was I could get a lifetime ban or even a two-year ban which at my age would have meant my career was as good as over.
"I have had 30 or 40 tests in my career and never tested positive. I have always been extremely careful about everything I have taken, and I didn't do anything differently before the Kessler fight."
Magee said he consumed the banned substance via a contaminated over-the-counter supplement he had been using to combat a cold. He is considering legal action against the supplier.
UK Anti-Doping accepted Magee's version of events, saying it was satisfied he had not sought to enhance his performance.
Magee's manager Pat Magee said he is currently in the process of contacting other athletes who may be at risk after using the same product, with a view to possible legal action.
Pat Magee said: "Brian is a clean boxer and I couldn't believe it when I was informed in February. It just goes to show you can never be too careful as far as these supplements are concerned."
The boxer, who fought Carl Froch in 2006 and is a former British and European champion, said he is intent on returning to the ring.
Magee added: "I've already got back in the gym and I can't wait to fight again. I haven't had any bad beatings and I think there are still a number of big fights out there for me."
His sample was submitted for analysis to the Norwegian Doping Control Laboratory, a World Anti-Doping Agency accredited laboratory and they reported that an adverse finding had been made on January 18.
The 38-year-old escaped a longer ban after managing to demonstrate the substance had been an unlabelled ingredient in a sports supplement he had used.
Magee declined to have his B sample tested. Magee's six-month ban began at the end of January meaning that he is free to return to the sport next week.
Magee, won two bouts for Ireland at the summer Olympics in 1996 before bowing out, won a bronze medal for Northern Ireland at the 1998 Commonwealth Games and silver medal for Ireland at the 1998 European Championships in Minsk, Belarus.
The banned drug oxilofrine that top Jamaican sprinters Asafa Powell and Sherone Simpson tested positive for last week is a stimulant used to boost the body's ability to burn fat.
The substance helps athletes boost their power-to-weight ratio with more lean muscle and less fat, and so increase their speed.
It may also increase the rate at which the heart reaches its maximum performance during exercise, meaning a greater supply of oxygen can get to the muscles earlier.
Oxilofrine is an agent that stimulates part of the nervous system and was previously used to treat low blood pressure. More recently, it has started to appear in combination with caffeine in dietary supplements marketed as weight loss products.
However, the superiority of using oxilofrine over an exercise warm-up to achieve this appears unconvincing.