Offenders allegedly took toilet doors off their hinges and are used them as weapons against staff.
The situation is ongoing and is expected to go into the evening. The prison or parts of the facility may be evacuated overnight, it reported.
St John staff are treating a number of staff and prisoners due to smoke inhalation. It's thought at least one prisoner is bleeding after an altercation with guards.
A prisoner on remand says a riot at the prison has been imminent, with prisoners protesting for basic human rights. They told Newshub of issues, including toilet paper taking days to be provided.
Three ambulances, 13 fire trucks, and police cars had arrived at the prison since about 5.30pm, Newshub says.
The Corrections spokesperson said the incident is contained and emphasised there was no threat to the safety of the public.
"We have comprehensive procedures for managing events of prisoner disorder," they said.
"Our Advanced Control and Restraint teams with specialist capability are on standby to assist if necessary. Our top priority is to resolve the situation safely."
Firefighters remain on site.
Last year, two Waikeria Prison Correction officers were punched in the face within nearly as many days, while fighting between prisoners has also been reported.
A prisoner punched an officer in the face and another officer was also injured when he stepped in to help.
The altercation comes after an officer was threatened and punched a few days earlier.
There had also been two reports beforehand of prisoners fighting among themselves.
Waikeria Prison is one of New Zealand's biggest prisons, located on a 1200ha site south of Te Awamutu in the Waikato region.
