Social Development Minister Anne Tolley says there will always be fights in prisons.

Social Development Minister Anne Tolley says plenty of service providers get into "difficulty" but that wasn't a reason not to offer them contracts.

Her comments were in response to the allegations and investigations surrounding private-prison operator Serco.

Earlier she had said that she was open to the idea of private operators becoming involved in more social services for vulnerable children and families, similar to social bonds.

Three Mt Eden inmates were among 10 people arrested in police raids on the Head Hunters gang - with police also talking to a former guard.

Under-fire Serco was looking at child services in the United Kingdom and Tolley said last month if private enterprise could deliver results, she "wouldn't hesitate" to use them.

However Labour MP Kelvin Davis said: "If Serco can't run prisoners in a prison how can they run services for children across the whole country?"

On Tuesday Tolley said the Government would be worried about any provider who was not performing well, "and we've got a number of those, whether they're private or NGOs (non-governmental organisations)".

"I think the quality of the contract is the really important thing - in the case of private providers we're wanting to see a bit extra and with any provider we want to see good control."

Corrections on Monday took over management of Mt Eden prison.

This was after Corrections chief Ray Smith and Corrections Minister Sam Lotu-Iiga last week invoked a "step-in" on the back of increasing allegations around fight clubs, contraband, drugs and "dropping" - a practice where inmates pushed other prisoners off balconies.

Tolley said fight club allegations had been around a long time - "not just in Mt Eden but in a number of prisons".

"These are prisons, they're highly volatile people you're dealing with.

"They're there because they're that sort of people and there will be fights, there's fights all the time. It's how the prison management reacts and the steps they take to prevent them."

Lotu-Iiga said the arrest of Head Hunter gang members in Mt Eden prison was "disappointing" and the allegations would be part of a review of the prison operations.

"It's too early to speculate about what we do in terms of Serco's contract but we've got a review in place. We need to get to the bottom of these facts before we make decisions."

He said the first part of the review would include the fresh allegations at Mt Eden and the second part of the review would investigate activities in all prisons.

Lotu-Iiga said he had been "reassured that it's going fine at Wiri" - a South Auckland prison also run by Serco.

He was expecting a report on Tuesday of all the contraband found in a full search of Mt Eden prison last week - the minister last week confirmed at least one cellphone had been found.

Davis, who has led the charge on many of the allegations being revealed at Mt Eden, said new information was still coming in.

A direct email line from Labour to the police was being set up to deal with a number of complaints and allegations being received.

"I think there needs to be a way for prisoners to voice their concerns safely and be taken seriously but what that looks like I don't know."

He said the review of Serco was due in about three months and he was cynical of the timing around that.

"It's probably going to be dumped on us, or released quietly I should say, on a Friday afternoon a day before the All Black semifinal or something and everyone's attention will be diverted elsewhere."