Workers are testing the air quality in the Reserve Bank's Wellington building after a trace of asbestos was found yesterday.
The building was closed and staff evacuated on Wednesday after the asbestos was found on level 1 of the building during a routine inspection.
It is now being remediated.
Three levels have been inspected, tested and found to be clear. Inspection and testing continues, while essential operations are being carried out at premises in Auckland.
"Because of the age of the building, asbestos must be presumed to be present. This is why we routinely inspect and conduct air monitoring across the building," head of communications Mike Hannah said.
"As a responsible employer and landlord, we decided to take the precaution of closing the building to inspect all levels and confirm that there is no risk to human health."
A plan is being developed for returning everyone to the premises after other levels have been inspected, tested and the safety of staff and tenants is assured.
"The safety of our people and tenants is our number one priority," Hannah said.
A spokesman yesterday said it was not known when the building would be cleared for staff to return.
The 14-storey building at No 2 The Terrace, across the road from Parliament, also houses the Parliamentary Counsel office, the Parliamentary Commissioner for the Environment, State Services Commission and the Defence Force.