It's claimed that an intoxicated fan was ejected from the stadium for throwing beer on Hopoate, his son and a Tonga team sponsor.
The Daily Telegraph reported that the former NRL bad boy did not instigate the alleged incident, where a Tongan supporter is alleged to have heckled Hopoate, an unofficial coaching consultant for Tonga.
It's understood that he told the fan to go away and sit down after being abused for several minutes during the Pacific test, which Samoa won 18-6.
Then the man is understood to have thrown beer, hitting Hopoate, his son and the team sponsor, before police escorted the fan out of Parramatta Stadium.
There are no suggestions of any physical contact between anyone and the NRL confirmed on Sunday night that it would launch an inquiry.
And a source is alleged to have told police that Hopoate has nothing to worry about.
"Hoppa told the bloke to stop being a bad sport - he was throwing beer and was intoxicated," the source said. "Trouble seems to follow Hoppa."