Saracens head coach Mark McCall says a comment to hooker Jamie George by one of Munster’s medics caused a brawl involving almost 30 players.
Assistant coach Alex Sanderson had told BT Sport during Saracens’ 15-6 Champions Cup win that it was related to George’s weight.
“As far as I know, one of their medical team said something which wasn’t all that good,” said McCall.
Champions Cup organisers are investigating the incident.
Munster say they do not know what caused the fight, while a statement from organisers European Professional Club Rugby (EPCR) said: “Information will now be sought from the match officials and from both clubs, and EPCR will be making no further comment until the investigation has been completed.”
The scuffle seemed to ignite Saracens’ attack and tries from Sean Maitland and Mako Vunipola helped the reigning champions to victory, keeping their quarter-final hopes alive.
“Whether the fight helped, I don’t know,” added McCall.
“The last 25 minutes of the match, we showed ourselves what we’re capable of. We’ve given ourselves a bit of a chance.”
Despite the loss Munster are second in Pool 4, one point ahead of Saracens, with French side Racing 92 six points ahead at the top.
The five pool leaders qualify for the quarter-finals, with the three best-placed runners-up also going through.
Saracens have a battle on their hands in the Premiership too, where they are bottom of the table on -18 points after a 35-point deduction.
But captain Owen Farrell says his side have not been distracted by the salary cap controversy.
“We’ve not been too fussed about the questions that have been asked about us,” he said. “We’re well and truly looking inwards.
“We’re rugby players. We’re nothing to do with what’s going on off the field. We’re nothing to do with what everyone is writing in the papers.”