When the alarm was activated, police were notified immediately.
Threats like this happened about once every couple of months, she said.
Ms Guard said the added security measures allowed staff to feel "a lot safer" as they knew there would be an "automatic response".
The added security in the centre also requires visitors to identify themselves through a speaker before entering the facility and corrections officers now wear stab-resistant vests with slash-proof gloves when dealing with offenders.
Opening in May last year, the facility also boasts 16 CCTV cameras throughout the building and two exit doors in interview rooms to make it easier for staff to leave threatening situations.
Minister Judith Collins said the features in the centre were "fantastic".
"Corrections has been taking safety for their staff really seriously but also for the public.
"Looking at all these mechanisms and things put in place all seem absolutely sensible but making use of all the technology as well."
She said it was important staff worked in a safe environment "given the fact they are dealing with offenders" in the community.
"It's already a difficult and, at times, a dangerous job, so we have to do our best to mitigate and, where we can, eliminate the risks," she said.
She wasn't surprised about the incident today.
"But what is really good here is they were able to use what they had to stop it going any further," she said.
"They are dealing with volatile people unfortunately, and they have to have the best mechanism to keep themselves safe."