England and Scotland must explain the tunnel fracas involving Owen Farrell and Ryan Wilson at Murrayfield on Saturday following a request for clarification by Six Nations Rugby.
The Rugby Football Union and its Scottish counterparts have been asked to provide clarification over the scuffle that took place shortly before Eddie Jones' men were defeated 25-13 in a pulsating Calcutta Cup match.
Television footage appears to show a clash between Farrell, England's inside centre, and Scotland number eight Ryan Wilson that ended when they were pulled apart by team-mates.
The incident unfolded as the players left the pitch and entered the tunnel upon completion of their warm-ups.
"Six Nations Rugby will be writing to the unions to request clarification on what happened in the tunnel," a Six Nations spokesperson said.
Once the unions have responded, tournament organisers will decide whether to launch an investigation or initiate disciplinary proceedings.
When the fracas was picked up by broadcasters during the interval, Martin Johnson quipped in his role as pundit that it was "England's highlight so far I think", summarising a dismal first half in Edinburgh.
Eddie Jones repeatedly denied knowledge of what had taken place, as did every player from both teams when asked for their account. Scotland captain John Barclay said he was in the toilet at the time.
"I've been coaching a game. I've been pretty busy. Are you aware of it? You can show it to me after the press conference, then we can have a chat about it," Jones said at the post-match press conference.
"In all seriousness, I don't know about it. If there was, we shouldn't let that detract from a great Scotland victory. Don't get distracted by other things."
When asked about the scuffle and whether it was evidence that England had lost their heads, Jones replied: "Look I don't know, I don't think so. These things happen."
Scotland captain John Barclay also played down the incident as he admitted he wasn't in the tunnel at the time.
"I heard about it but I am always the first off the pitch after the warm-up and I was in the toilets," said Barclay. "It is one of those things that gets built up into something more than it was. It is a big game and a big rivalry. It was niggly and physical with a lot on the line."