He understood that an adult from the Ponsonby team had "manhandled one of our kids".
He was stopped by the mother of the child, and there was an "altercation" between the two, Mr Mallabar said.
However, he stressed he had only read one report into the incident.
"Until you hear both sides, you don't know."
Waitemata's junior club captain Josh Hyde and the Ponsonby coach calmed the situation down, Mr Mallabar said.
"There was some verbalness between parties - there was eight minutes to go or six minutes to go - and that was it."
It was disappointing when these incidents happened, he said.
Mr Mallabar said he wanted to get a sign for the field reminding parents the game was for children and was not a World Cup match.
The Auckland Rugby Union "swamped" clubs with information about fair play, he said.
"I'd hate for rugby to be tarnished over one incident where someone's just got carried away and has seen something where their kid has got affected and they've run on without really engaging their brain and then somebody else has run on because their little Tommy is being manhandled."
Ponsonby's chairman of junior selection Brent Metson said he was aware of the incident.
"The respective club delegates are looking into the matter and I can't comment any further until they've had their investigation."
Auckland Rugby Union confirmed it had received reports about an alleged incident at the under-8s game on Saturday between Ponsonby and Waitemata.
"An incident occurred that started on the field and then I believe spectators got involved but I don't know the extent of it," Auckland Rugby communications manager Libby Gudmundsson said.
"We have had reports from both clubs now. It's just a matter of going through this and making sure we have a clear picture of what happened."
Miss Gudmundsson said it was important to establish the facts as the union did not send match officials to under-8 grade games.
"So it's going to be what the opposing clubs say. We need to get a clear understanding before we know whether we need to take it further."
It's not the first time spectator's tempers have flared at rugby matches. Four Auckland Grammar and five Kelston Boys' players were banned in 2009 after scores of spectators waded into an on-field brawl between the boys.
Police were called after a referee was punched in the face, allegedly by a spectator, at a rugby final between Auckland Grammar and De La Salle College last August.
In June, two Porirua men attacked supporters and the coach of the opposing team at an under-11 game. The previous month a parent grabbed the ref's throat at an under-10s match in Papatoetoe.
In 2011, five Otahuhu Rugby Club players were banned for life after assaulting a whistler at the conclusion of an under-19s match, Hawke's Bay Magpies mascot Kahu the Magpie kneed her Bay of Plenty Steamers counterpart Hori in the groin in an ugly sideline clash.
-Additional reporting New Zealand Herald.
