Penrith officials and the NRL have begun investigating the foam football throwing incident that marred Parramatta's win over the Panthers at CUA Stadium Saturday night.

Referee Ben Cummins was struck on the head by a mini football as he was being escorted from the field at fulltime after the Eels' 26-18 win, with police reportedly ejecting the fan who threw the football.

Panthers officials have already begun their investigation, with the NRL to address the issue Sunday as part of their weekly review.

"It will obviously be part of our normal post-match investigation and review that we will conduct (on Monday) and we will talk to the Panthers about it and the security measures," said NRL chief operating officer Graham Annesley.

It is the second time this season a Panthers fan has thrown a foam football onto the field at CUA Stadium, with an incident also occurring in the club's home game against Canberra in round two.

On that occasion, a football was thrown at William Zillman as he dived over for a try although the Raiders fullback was not hit.

Panthers coach Matt Elliott called for the fan to be banned for life from NRL matches.

He was also critical of the performance of Cummins and his fellow match officials, saying they should be "disappointed" because of a couple of questionable calls against both sides.

But referees coach Robert Finch said he was "comfortable" with the officiating.

"They were fine," Finch said.

"Just briefly looking at the debrief, which we'll look at more closely (Monday), at this point in time I'm quite comfortable with it."

Elliott, in particular, queried two decisions either side of halftime when his side were ahead 14-6.

The first saw Panthers backrower Nathan Smith denied a try after Cummins ruled he had been held up over the line. Cummins had referred the decision to the video referee, but Graeme West sent it back to the on-field official.

On that ruling, Finch said: "The touch judge was in line and he made the call of held up, and there was no evidence to say that he was wrong. That's why it went back to ref calls."

Panthers hooker Luke Priddis then looked to have scored an amazing length-of-the-field try five minutes after halftime following a break from winger Michael Gordon, only for Cummins to call the play back for a 20m restart after ruling Gordon had caught a Brett Finch kick in his in-goal.

Gordon had one foot either side of the tryline when he jumped to take the kick.

Finch said the ruling was again right.

"If you have one foot on the line or in-goal when you have left the field then you are in the in-goal so as soon as he catches the ball from the in-goal it's a 20m restart," he said.

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