Celtic have been asked for their comments by the Scottish FA about goalkeeper Artur Boruc's raising of a "champions" flag at Ibrox on Saturday.
Artur Boruc kept the Celtic flag flying at Ibrox
It follows the inclusion of the incident in referee Craig Thomson's report to the governing body.
But Boruc told Celtic TV: "I'm the champion and I wanted to show that to everybody. If it was Ibrox, sorry.
"It was simple. I was just celebrating that we are the champions. I don't see anything weird with this."
Some Rangers fans were angered after the 27-year-old Poland international took the flag from a Celtic supporter and waved it on the pitch after the match.
Strathclyde Police had stated: "We are aware of the Celtic goalkeeper's actions at the end of the game.
"No criminal act has occurred, but we will be addressing the matter to Celtic and the Scottish Premier League."
Thomson pointed out in his report that the police had advised him of Boruc's actions.
And the SFA could charge the goalkeeper with misconduct should it be disatisfied with Celtic's response to their letter.
Boruc received a procurator fiscal's caution for breach of the peace in August as an alternative to prosecution after making gestures at Rangers fans at Ibrox in February 2006.
And Dundee United fans last month complained that the goalkeeper made a gesture at half-time during their game against Celtic.
But Celtic manager Gordon Strachan, interviewed after Saturday's game, dismissed the suggestion that that the latest incident had constituted a provocative gesture.