SOUTH SYDNEY officials believe they are closing in on the rogue supporter who hurled a metal socket at Manly centre Steve Matai on Sunday - but have urged the offender to save them the trouble by putting their hands up and coming forward.

Even though they have been unable to identify the fan through CCTV footage, chief executive Shane Richardson said the club fielded several phone calls from members with leads as the NRL threatened a minimum five-year ban for the person.

In making his plea to the members, Richardson said the club's supporters had been instrumental in identifying a fan who through a bottle at referee Jason Robinson at the SFS in 2005 in a match against Canberra and he was confident the latest antagonist would be found via the same channels.

"They really care about their image," Richardson said. "We'd like them to come forward with information. We can't pick it up on CCTV but we'll find out one way or another.

"It's not the sort of thing you want to be associated with. One person creates a problem in a crowd of 11,000 so you do everything you can to find them. But I'm hoping the guy steps forward. It's one of those things, if a group of players got named, everyone gets tarred with the same brush. But from our point of view, we'll keep on it until we find him."

ANZ Stadium officials, police and the Rabbitohs have all studied the venue's security footage but have been unable to pinpoint the object being thrown at Matai, after he was sin-binned for a professional foul late in the first half of South Sydney's upset victory over the Sea Eagles.

After launching their own investigation, stadium officials found that the offending projectile was brought into the ground rather than taken from the structure itself.

Manly chief executive Grant Mayer demanded that an example be made out of the fan.

"It's bloody dangerous, unbelievably dangerous, and extremely serious," Mayer said. "We all love our football and emotions are a key component, but when it comes to people throwing metal objects, that takes it to a new level. We need to make examples out of these guys.

"It was obviously a brain snap of the highest order. Hopefully they're identified and a written apology is given to the club and to Steve Matai, and then they're banned."

Mayer spoke with Richardson yesterday and, even though the CCTV footage had given them a dead-end, was confident the Rabbitohs were doing all they could to identify the offender.

"They've reacted to our concerns and I take my hat off to them," he said. "They're doing the right thing, because it tarnishes the brand. It's about trying to protect their club from anti-social behaviour."

While the latest incident follows two others in the past year - coins being thrown at another Manly player, Jamie Lyon, on his return to his former club Parramatta, and racial taunts being directed at Penrith skipper Petero Civoniceva at the same venue - the NRL believe the case is an isolated one, but will still come down hard on the person if they are identified.

"The NRL remains firmly of the view that if the offender is found, they will be banned, and it will be a long time before they set foot inside another venue," NRL chief operating officer Graham Annesley said.

"Souths have taken it extremely seriously and are working not only with the stadium but also the police. As in all of these investigations, they're limited by the evidence available, but they're continuing to investigate.

"Whenever you're in a large public venue, short of having the perimeter of the ground screened off with perspex, there's always going to be the opportunity for some lunatic to do something outrageous. We don't have a pattern of that happening but you can't guarantee that occasionally there won't be some person who oversteps the mark. But we will deal with them harshly."

Souths issued their plea with a statement on the club's website which condemned the actions as "foolish … on what otherwise was an outstanding day for the club".