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.
"Air quality testing was carried out which led to the discovery of higher spore counts than acceptable indoor level guidelines."
Chenery said that so far the reduced number of cells had not been a problem.
"There are other options we have available within existing resource, and with the number of cells we still have operational this has not been an issue."
He said the health and safety of staff remains a priority, and is being actively managed through ongoing air quality testing and regular cleaning of the cells.
New Zealand Police Association President Chris Cahill said the problem had already been bad enough before the flooding.
"This has compounded a dire situation as this custody unit was already far from ideal and is one of a number that the association has advised police needs urgent attention."
Cahill says the Nelson Police Station is generally past peak performance, but the cost of replacement is significant and comes at a time when remedial work is needed to strengthen the Blenheim police station to meet seismic strength thresholds.
The Nelson and Blenheim police stations are within the Tasman Police District. Cahill says the work needed on each has contributed to pressures for police in the region.
He says outdated and unsafe custody units are "quite widespread" throughout New Zealand and is an issue that will require a considerable amount of work involving the wider justice sector.
"The association is seeking clarification from police on their plan to address the immediate concerns with the Nelson custody unit," Cahill said.