Custody cells at the Nelson Police Station have been closed because of harmfully high levels of mould.
Recent flooding in Nelson has compounded what the Police Association says is a "dire" situation in the custody unit of the city's central police station.
The police station was built in 1961 for $75,000 and the cell block was listed as its most significant feature at the official opening.
Acting Area Commander Detective Inspector Mark Chenery told Open Justice that recent heavy rain had leaked into the building's roof cavity, and some of the 16 custody cells have been closed while remediation options are considered.