Police investigating allegations about a group of men called Roast Busters have spoken to two men alleged to have been involved.

The group of Aucklanders, thought to be aged 17 and 18, film their sexual exploits with drunk teenage girls and post the footage online. Victims are understood to be as young as 13.

Police investigations over the past two years have not resulted in any charges being laid.

As the case today dominated news and social media discussions, a man who had previously declined to co-operate went into a police station.

Another man is also being interviewed by police, Detective Inspector Bruce Scott said.

He said the investigation was making progress, but it was too soon to say if ''this development'' will result in any prosecution.

"We're grateful that the publicity around this case has enabled us to make further progress, and we hope to build on the work done by the enquiry team to potentially take us to the stage where we have enough evidence to build a case."

Prime Minister John Key condemned the alleged actions of the Roast Busters gang as "extremely disturbing and disgusting behaviour".

"These young guys should just grow up," Key said this afternoon.

"I guess, as a parent, I find the issue very disturbing and abhorrent really.

"I mean, you are talking about youngsters who are at a very delicate age."

"These young guys should just grow up," Key said this afternoon.

Key defended the work of police.

"It is very difficult to progress this issue, if someone isn't prepared to make a formal complaint.

"And it's a very challenging situation for a young woman to put herself in that position."

Key said that under a proposed law, the online bragging would be classed as cyberbullying and would be unlawful.

The Harmful Digital Communications Bill is yet to be introduced to Parliament.

Asked if Facebook should have acted to remove the sites, Key said the Government needs "to continue to look at those matters", but it is "more for the Government to try and set boundaries".

Police were criticised for leaving the Roast Busters Facebook page open, Scott said.

"The page was left open for operational and tactical reasons, and whilst we acknowledge it was upsetting for the victims, it was being monitored for information or evidence that would assist our investigation."

Police had contacted possible victims as recently as two weeks ago and interviewed suspects.



Detectives alerted the high school the suspects were attending, and in a statement today, Waitemata police vowed to keep investigating to build a case.



An inquiry team had worked tirelessly for months on the case, and offenders and circumstances had been identified, they said.

A "full and thorough" investigation had been carried out but without more evidence, such as formal statements from victims, police were unable to prosecute.



"Detectives from the Waitemata child protection team have been working on the case since 2011, when a teenage girl came forward to police to informally report what had happened to her," police said.



"Three teenage boys were formally interviewed by police as suspects, but unfortunately made no admissions. A fourth boy refused to co-operate."



All identified and possible victims were contacted by police and encouraged to give formal statements.



"We appreciate their difficult and traumatic situation, however without further evidence such as formal statements police are unable to prosecute the offenders in this case," police said.



"In the past two weeks, police contacted the girls again to see if any were at the stage where they felt able to make a formal statement to police, and will continue to investigate this case and to build sufficient evidence to progress this matter."

'HUGE CONCERN'

Meanwhile, Rape Prevention Education executive director Dr Kim McGregor said that if media reports about the Roast Busters were correct, what they were doing was "absolutely rape".



"Some of the girls are children, they're only aged 13 so that's rape. Even if you're over 16 and having sex with people who cannot give consent because they're stupefied by a drug, that's rape."



The attitudes of the men involved were a "huge concern" and unfortunately widespread, she said.



"They have been saying it makes them feel like a man, and talking about women not as humans but as boasts - dehumanising them. I hope men's groups are stepping up to address this."



The group started a Facebook group five months ago and have been calling for other men to join them, 3 News reported. The Facebook page has since been taken down.



"We take what we do seriously, some of you think this is a joke, it's not," said one of the men in an online video.



"You try and get with the amount of girls we do. This is hard, it's a job, we don't do this s... for pleasure."



One underage girl who spoke with 3 News said she was a victim of the Roast Busters.



"I just kept blacking out 'cause I had drunken too much," she said. "You could say I got raped. I had sex with three guys at one time."