Three players saw red following a half-time brawl in 13-man Grenoble's 36-23 Top 14 victory against Brive in an ill-tempered match at the Stade des Alpes on Sunday.
Sona Taumalolo and Nigel Hunt of Grenoble and Brive's Damien Jourdain were dismissed amid a mass confrontation between both sets of players, with staff and substitutes also appearing to become embroiled in the violent scenes.
While only three players were given their marching orders, retrospective action could well be taken against others seen throwing punches.
After Benjamin Lapeyre dabbed down to put Brive ahead after 15 minutes, Grenoble took charge of the match through scores from Taumalolo and Charl Mcleod before tempers flared when the hosts turned a Brive scrum and forced them over the sidelines after the 40th minute.
The ensuing melee resulted in dismissals for Taumalolo, Hunt and Damien, and the second half continued to prove fiery.
Karlen Asieshvili's try brought Brive to within three points, but they lost Julien Ledevedec to the sin bin on the hour and Grenoble responded through Armand Batlle, who appeared to receive an eye gouge from Matthieu Ugalde that went unpunished as he touched down.
Both sides ended the match light of a further player with yellow cards to Ali Oz and Kevin Buys inside the final 10 minutes, and Grenoble apologised for the scenes following the match.
"FC Grenoble Rugby wishes to express its apologies to fans and viewers of the match. The images seen on the Stade des Alpes pitch does not correspond to the view of rugby that FC Grenoble Rugby, its directors, its staff and its players hold," an official statement said.
Comments attributed to Taumalolo and Hunt by Grenoble read: "We offer our apologies to our team-mates and to all supporters of FCG. We thank and congratulate all the players who were able to win the match despite our red cards."
Toulon bounced back from defeat to Brive last time out with a bonus-point 32-15 victory over Toulouse at the Stade Ernest-Wallon.
Tries from Guilhem Guirardo and Axel Muller were added to by Charles Ollivon in the 79th minute.