A TVNZ spokesperson confirmed there had been a "building intruder late last year".
"Our perimeter security systems have since been strengthened to prevent this happening again. We take our responsibility [to] keep staff, and their cakes, safe very seriously."
Earlier this year, the last 10 minutes of the nightly current affairs show Seven Sharp co-hosted by Jeremy Wells and Hilary Barry went off air after TVNZ HQ had to be evacuated after a fire alarm.
Viewers were instead shown a replay of Kiwi Living during the May 14 incident.
TVNZ confirmed at the time that fire alarms were activated after it appeared an appliance in the tea room had over-heated, generating smoke.
A spokesperson said a review would be carried out so that the network could "take steps to avoid a repeat".
And last year a small electrical fire led to the newsroom being evacuated and 1News' 6pm bulletin delayed for half an hour.
The fire had started in the building's server room, with nine fire appliances responding to the incident, leading to a road closure.