Latrell Mitchell has also demanded the NRL take action, posting to Instagram: "I stand with you Bala. (The NRL) better deal with this s**t".

Indigenous star Mam could be heard telling referee Adam Gee, "He called me a monkey", as other Broncos players also say, "He called him a monkey".

Gee said he did not hear the alleged slur himself, and asked Mam if he wanted to make a formal complaint, to which Mam responded: "Yes I do".

When placed on report by Gee, Leniu can be heard saying to the referee: "Why would I say that?".

Leniu told Triple M after the match that he was not "worried at all", and that the incident was "just fun and games on the field, that's it".

But Broncos coach Kevin Walters said Mam was certain a racial slur had been made.

"He's pretty upset in there," Walters said. 

"He's adamant (there was a slur), but we'll leave it with the NRL. They're looking at it.

"We certainly support Ezra and our player and everything that's around that."

Broncos captain Adam Reynolds said he personally had not heard the slur, but was shocked by the allegation.

"In this day and age, you wouldn't think this is still out there," Reynolds said.

"I was well away from it. But we support our player. He is pretty upset in there. 

"We certainly don't stand for racism and we'll support Ezra and get around him, make sure he's alright."

Sydney Roosters coach Trent Robinson said he had not spoken to Samoan Test representative Leniu about the allegation yet, but said it was important a process was followed.

"He obviously made the complaint, but that doesn't mean that it's right," Robinson said. 

"It'll go through the formal process as it should."

The incident came in a brutal but entertaining win for the Roosters to start the season, in front of 40,746 fans at Allegiant Stadium.

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