Michael O'Reilly is understood to have asked to have his B sample tested in an attempt to have the provisional ban which is preventing him fighting in the Olympics lifted.
Earlier this afternoon his legal representatives lodged his case with Sport Ireland.
It had been thought the most likely course of action was to appeal his provisional ban on the basis of inadvertent use of a prohibited substance.
However, a request to have the B sample tested would imply that the 23-year-old middleweight believes the positive test on the A sample was incorrect.
Any test on the B sample is likely to take a number of days to conduct.
O'Reilly is due to fight in the Olympics on Friday.
