Australian taxpayer-funded built facilities at the Nauru immigration detention centre rotted with mould and, in some cases, staff stepped through the floor.
Staff at the Nauru immigration detention centre developed health problems from mould exposure in Australian taxpayer-funded buildings which were "rotting from the inside out."
A 15-month investigation by AAP can reveal air-conditioning caused water damage and mould to grow in the fire-resistant plasterboard walls and ceilings and the magnesium oxide board floors of modular staff buildings since 2013.
It's understood at least a dozen former centre workers exposed to mould in their bedrooms have developed conditions including toxic mould syndrome, cognitive and neurological symptoms, chronic pain, chest infections, and persistent coughs.
A source familiar with the problem said the buildings had been "rotting from the inside out" and people's feet had broken through the floors at Regional Processing Centre 1 which housed staff accommodation, the kitchen and mess hall.
The source said authorities at the centre blamed the health issues on passing phosphate trucks.
"Once the rectification started and they pulled the sheets off the walls to replace it, it was discovered that the fire-rated board was completely compromised due to rot and severe mould," the source said.
"In the event of a fire there's a very real risk of casualties."
The Nauru detention centre had burnt down following a 2013 riot and rebuilding has cost taxpayers $356 million.
The same modular buildings were used in the Nauru hospital upgrade and community centre where there were also mould problems.
The source said building contractors had opted for a band-aid solution to fix the problem.
"They polished a turd," the source said.
But construction company Canstruct defended the fire resistance of buildings it installed on Nauru saying they complied with relevant Australian building codes and standards.
"No corners were cut at any stage," a company spokesman said.
The source said one of the building contractors was "somewhat commercially exposed" so a decision was made to repair small areas that were most visual "at a cost-plus variation to the contract".
AAP obtained a leaked email from a project manager with construction firm Canstruct which said minimum solutions were being sought and staff with knowledge of the extent of the problems had been "gagged".
The source said mould expert Jeremy Stamkos was hired to travel to Nauru to inspect the problem and devise a plan to fix it but his second trip was cancelled by "panicked" high-level stakeholders.
Canstruct disputes any claim Mr Stamkos was blocked from returning to the island and says he was involved in rectification works.
When asked about the mould problem on Nauru, Mr Stamkos told AAP he was "not authorised to talk" about the matter.
Minutes of meetings from December 2015 between the Immigration Department (now called Home Affairs), construction firm Jacobs and Canstruct, which AAP obtained under freedom of information laws, blamed the deterioration of floors in the mess, kitchen galley and cold store area on "heavy traffic".
The Home Affairs Department insisted the construction procurement process at Nauru was done in accordance with legislation and procurement rules.
The Australian Greens have called for an urgent investigation by Comcare, the public service workers compensation authority.
"The government has abjectly failed in its duty of care," Greens senator Nick McKim told AAP.
The Nauru government said it was unaware of any problems with construction projects on the island.
Comment has been sought from Jacobs.