A Corrections officer thought they were going to die during a "savage, violent" attack that left four Otago Corrections Facility staff needing hospital treatment. 

A review would be carried out following the attack in a high-security unit on Saturday afternoon, prison director Lyndal Miles confirmed. 

Two prisoners initially approached two staff in the unit's staff base and began assaulting them, Miles said. 

Two other prisoners then joined in the assault as additional unit staff came to assist. 

"Other staff responded quickly to help bring the situation under control." 

Four staff were injured and taken to hospital for assessment but were discharged later that day and "are all keen to return to work", Miles said. 

Otago Corrections Facility director Lyndal Miles. Photo / Supplied, Otago Daily Times 

"They have the full support of prison management and welfare support services, and other staff have been checking on them regularly." 

All four prisoners had been placed in directed segregation and would be charged with misconduct, she said. 

Police were advised of the assault and would determine whether any criminal charges were laid. 

She could not provide any further information on the injuries suffered by the staff members for privacy reasons. 

Corrections Association vice-president Paul Dennehy said that a colleague who viewed footage of the incident called it a "savage, violent assault". 

One of the injured staff members told a colleague they thought they were going to die "because of the sheer brutality of it". 

Corrections Association vice-president Paul Dennehy. Photo / Brenda Harwood, Otago Daily Times, File 

There was concern about one of the officers suffering a concussion, and other injuries to an arm and a nose, Dennehy said. 

It was unclear what had sparked the attack, he said. 

One of the responding officers managed to use their pepper spray during the incident. 

He believed it was the most significant mass-injury assault at the prison since 2017. 

The association was engaging with Corrections over the incident and why it occurred. 

That would include looking at whether there were any red flags in terms of the prisoners in the unit at the time, and also the security of the staff base. 

The staff base was a slightly raised desk area where staff could engage with prisoners. 

"It's not an impregnable position," Dennehy said. 

Miles said Corrections staff worked in a complex and challenging environment with a unique set of risks. 

"They manage some of the most dangerous people in New Zealand, many who are highly vulnerable with complex mental health and alcohol and drug issues. 

"Assaults on Corrections staff are unacceptable and any prisoner found guilty of an assault will be held to account for their actions. 

"As the police investigation remains ongoing, we're not able to comment further." 

Figures released to the Otago Daily Times earlier this year showed in the 2019-20 year, there were three serious assaults on Corrections officers at the Otago Corrections Facility, as well as 10 non-serious assaults and 21 no-injury assaults. 

Corrections recorded health and safety incidents on a tracker system. That included events involving prisoners, staff and contractors, and tracked any injury incidents, non-injury (near-miss) incidents and events related to uncontrolled hazards. 

There were 680 events recorded on the health and safety tracker at the Otago Corrections Facility between January 1 and November 30 last year. 

- Daisy Hudson, ODT