A member of the Guam national mens kayaking team tested positive in a random drug test last month.
Guam Kayak and Canoe Federation president Joe John Mantanona told the Pacific Daily News that although the drug was not illegal, it is an illegal stimulant that cannot be used during the games.
Mr Mantanona says the athlete in question has since admitted to using the performance enhancing drug.
The drug tests were conducted during the 2011 Pacific Games in New Caledonia.
Penalties are currently being discussed between the Pacific Games Council and the World Anti-Doping Agency.