London - Six Nations chiefs have still to make a ruling on whether improper substitutions took place in last month's France and Wales clash with the controversial closing stages now under review.
The March 18 match in Paris ended in a 20-18 win for France, with referee Wayne Barnes allowing an extraordinary 20 minutes of added-on time at the end of the game.
With France 18-13 behind and camped on the Welsh line, a series of scrums took place late in the match as they went in search of an equalising try.
In the midst of this, France prop Uini Atonio was replaced -- despite telling Barnes he was not injured but his back was hurting -- by preferred tighthead prop Rabah Slimani, known for his devastating scrummaging power.
France coach Guy Noves insisted it was a genuine call by his medics under the head injury assessment (HIA) procedure, which would leave Barnes with no choice but to allow France to bring back the previously substituted Slimani under rules governing the treatment of suspected concussion.
But Wales caretaker coach Rob Howley said there was "evidence to suggest that the integrity of the game has been brought into disrepute" by France fabricating the head injury call.
Monday's Six Nations statement, rather than drawing a line under the incident, instead promised a new inquiry.
"Following its preliminary investigation into the replacements made in the latter stages of the France v Wales match on 18 March 2017 (and in particular the replacement of Uini Atonio by Rabah Slimani), Six Nations Rugby has decided to refer the matter to the independent Six Nations Untoward Incident Review Group (UIRG) for review."
The statement added: "Six Nations Rugby will send the file to the UIRG later this week and it is anticipated that the review process will begin shortly thereafter."
The UIRG came into being a couple of seasons ago when the HIA procedure for dealing with suspected concussion was introduced.
Officials have already decided they will take no further action against France wing Virimi Vakatawa, sin-binned for a high tackle, and not pursue a biting complaint from Wales wing George North for lack of evidence.
Last week, France vice-captain Yoann Maestri was fined 30,000 euros ($32,000) for a post-match criticism of English referee Barnes where he said: "Anglo-Saxon referees always talk about fair play but the reality is that they think we (the French) are cheats."