Athletes are being warned of the dangers of taking supplements and medications which may contain banned substances without their knowledge.
Delegates at a world anti-doping conference in Auckland say products which promise to increase muscle growth and stamina can sometimes include steroids which are not named in the list of ingredients.
One of the groups attending, Drug Free Sport, fears more athletes could be banned if they are not educated on the dangers of using supplements and medications.
Drug Free Sport says some athletes are testing positive despite not attempting to cheat.
Chief executive Graeme Steel says inadvertent or ignorant doping is a big problem, and can come from medication or supplement use.
Mr Steel says some supplements can be tainted with banned substances which would cause athletes to fail drug tests.
He says the supplement industry is growing, and it's becoming more and more attractive to athletes.
About 30 organisations from around the world are at the conference.
