Corrections officers barricaded themselves and a prisoner inside a van after its tyres were slashed and shots fired at a tangi in Waikato.

A minimum security prisoner had been given permission to attend a family member's funeral at a marae on Thursday afternoon, and was escorted there by corrections officers from Waikeria Prison.

Police say most of those attending the tangi were gang members.

At about 12.45pm, a shotgun was fired into the air several times.

Waikeria Prison general manager Rosemary Firth says the guards immediately returned to the escort vehicle, only to find its tyres had been slashed. They locked themselves inside and called for help.

"The tyres of the prisoner escort vehicle had been damaged, so they secured themselves and the prisoner inside the vehicle while additional staff and vehicles from the prison were immediately dispatched to the area. All staff and the prisoner safely returned to the site without further incident."

The corrections officers involved had shown "exceptional courage", Firth says.

"Our staff did an excellent job responding to a incredibly challenging situation and I would like to acknowledge them for their professionalism and bravery. They moved swiftly to secure the prisoner to ensure no risk to public safety and their actions ensured the safety of the prisoner and their colleagues.

"Threats and intimidation towards our staff are unacceptable, especially when they're trying to do the right thing by allowing a prisoner to mourn the loss of a loved one."

Police say a shotgun shell was found near the Department of Corrections' van, and enquiries are being made to identify and find the person who pulled the trigger.

Waikeria Prison was currently undergoing a large redevelopment project, which has been pushed back several times. It was where New Zealand's biggest prison riot happened over the 2020/2021 New Year period, when 17 inmates burned a high-security unit to the ground, in protest over "inhumane" conditions.

-RNZ.