Dunedin's Mangu Kaha kingpin Albert Epere is one of those under the police spotlight after a prisoner was critically injured at Otago Corrections Facility last week.
An assault in an exercise yard at the prison on Friday afternoon resulted in the injured man being rushed to Dunedin Hospital with critical injuries.
He remains at the hospital in a serious condition.
While Epere is not suspected of causing the injuries, it is understood he is one of several Mangu Kaha (Black Power) members to attract police attention after the assault.
Epere is on remand at the prison.
The Mangu Kaha associated trust, Mauri Kohatu Incorporated, was awarded a Dunedin City Council contract for litter and weed control in 2015 after Epere pleaded his case to councillors, telling them he wanted to leave his life of crime behind for his family's sake.
The assault in Otago Corrections Facility is the latest in a spate of gang-related violence in Dunedin and its surrounds.
Ten staff from Dunedin and Balclutha's CIB are investigating the assault, Detective Senior Sergeant Hayden Smale said.
"The assault occurred in an exercise yard at the prison and involved members of the Black Power gang," he said.
"The victim is not linked or involved with this gang.
"It is too early to comment on the nature of charges that may be laid or the number of individuals involved while the investigation is ongoing."
Prison director Lyndal Miles confirmed one prisoner had been placed in directed segregation following the assault.
Corrections would not comment on whether any further sanctions were possible for others present when the assault occurred.
"Staff responded immediately to provide the victim with medical assistance and he was transported to hospital," she said.
"The alleged perpetrator was removed from the unit and placed on directed segregation.
"Violence in prisons is unacceptable. Gang prevalence and influence is a contributing factor to the rate of violence in prisons.
"Prisoners who use violence will be held to account for their actions."