Tunisia's Football Federation say it did not treat Brazilian-born striker Francileudo dos Santos with corticoids during the recent African Cup of Nations.
Traces of corticoids, steroid hormones which reduce fatigue and swelling, were found in Santos' urine following a medical check-up at his French club Sochaux.
The tests were taken just two days after the striker returned from the Nations Cup in Tunisia.
Santos helped his adopted homeland lift the trophy with a goal in the final as they beat 2-1 Morocco two weeks ago.
Hamouda Ben Ammar, the president of the Tunisian Football Federation, says that Santos was not given corticoids by the Carthage Eagles.
"He did not receive any special treatment as far as I know," Ammar said.
"He was tested after the African Nations Cup final and the test proved negative.
"The doctors of Tunisia and Sochaux are in contact to clear up the case."
Corticoids are permitted under prescription and if certain rules are followed on how they are administered.
Santos did receive treatment for a hamstring injury while he was in Tunisia and Sochaux president Jean-Claude Plessis says that they are waiting for details of the prescription for his treatment.
Sochaux have already withdrawn the striker from the French club's Uefa Cup third round first leg match against Inter Milan last week as well as Sunday's league encounter with Bastia as a precautionary measure to avoid a positive dope test.
Santos had another internal test with Sochaux last Friday, with the results expected in the next few days.
Tests conducted by Fifa do not necessarily look for corticoids, but this is not the case in France.