The UFC's traditional pre-pay per view press conference was unexpectedly cut short on Thursday, with president Dana White telling the media he has never seen anything like the fight which broke out backstage.
It is being reported by Ariel Helwani that while fighters were waiting backstage before being brought out, welterweight fighters Kevin Holland and Khamzat Chimaev exchanged words, before things turned physical with their entourages getting involved.
Helwani also reported that Nate Diaz – Chimaev's opponent this weekend – and his crew got involved after things kicked off, describing it as "total chaos".
Addressing the media before word had spread about the incident, White said "this has never happened in the history of this company", before adding "for everybody's safety, this is the right decision".
In an interview after the dust had settled, White offered some more insight into the severity of the situation.
"22 years I've been doing this – we've never had an incident like today," he said.
"All hell broke loose out here… we stopped it, but we didn't do a good job of not letting it happen.
"It's never happened before, and we'll be ready for it next time."
Journalist Helen Yee added that White claimed the camps travelling with Chimaev and Diaz consisted of at least 100 people, rendering their limited security helpless.