There's good news for people arrested in Nelson – you won't be spending a night or two in the cells there. 

The bad news is you might find yourself being driven many miles away instead. 

The cell block, which holds overnight arrests and remand prisoners at the Tasman Police District Headquarters, is closed - for the time being at least. 

Prisoners are now being driven to other police centres within the vast police district which covers about a third of the South Island. 

Open Justice reported in March that some of the 16 custody cells at the Nelson Police Station had been closed while a solution was sought to fix harmfully high levels of mould, after heavy rain had leaked into the building's roof cavity. 

Air quality testing revealed higher spore counts than acceptable indoor level guidelines, which was a problem for those detained and staff working in these areas. 

New Zealand Police Association President Chris Cahill said the problem was already bad before the flooding. 

The cell block at the Nelson Police Station has been closed because of harmfully high levels of mould. Photo / Tracy Neal 

The entire cell block was now closed, along with offices within the building which housed the district's main police station. 

Acting area commander Senior Sergeant Martin Tunley told Open Justice the problem was limited to the cell block and a few other smaller areas within the building, but as a precaution several offices had now also been closed. 

"Any risk to staff has been mitigated by temporarily closing or limiting access to parts of the building while we treat and await test results," Tunley said. 

He said driving detainees outside Nelson to other areas was a logistical challenge at times, but the safety of staff and those in their care was paramount. 

The Police Complaints Authority, which monitored places of police detention to ensure human rights standards were being met, was aware of the issues with the custody unit in Nelson. 

The Tasman Police District covers a 70,000 square kilometre territory, across the top of the South Island to Kaikoura and down the West Coast of the South Island to Haast. 

The Nelson Police Station was built in 1961 for $75,000 and the cell block was hailed at the official opening as its most significant feature. 

The Nelson Police Station is HQ for the Tasman Police District, which covers a third of the South Island. Image / NZ Police 

Tunley said other high-use areas of the station had been tested and the results had come back within safe levels. 

"Ensuring the cell block is fully operational again remains a priority and we continue with a regime of testing, treating, cleaning and improving the air flow until the matter is resolved," Tunley said. 

He said recent lower reading of mould levels post treatment meant the cells were able to be used in a "very limited capacity" last weekend. 

The Police Complaints Authority manager Stu Graham said it had recently completed an inspection of Blenheim and Nelson under its designation as the National Preventive Mechanism and had discussed its concerns with the police. 

"We are working with police to ensure that the facility, conditions and treatment of people detained and held in custody in the Nelson area meet the appropriate standards. This includes the transportation of people," Graham said. 

- by Tracy Neal, Open Justice