About 40 staff at the Blenheim police station have had to move to safer areas of the building after parts of it were deemed too dangerous to occupy.
A seismic assessment of the station found the cellblock, and an addition that sits directly above it, are unsafe.
Acting Tasman District Commander Inspector Gini Welch says those in custody are also being shifted.
"All people that are in our custody... will be transported to Nelson. We'll continue that for the foreseeable future."
Welch says they have two options.
"The first option is to strengthen the existing building. The other option is to pull it down and rebuild a new building on top of the existing cells."
The front counter remains open.
Welch says the building has been undergoing assessments since the Kaikoura earthquake.
"The engineers came back for some more in-depth and more invasive testing, which takes some time because it's all about watching how the building moves in response to environmental changes. The eventual findings we received yesterday."