The Government's workplace safety agency has told KiwiRail its investigation into workers being exposed to toxic gas fumes in the country's longest rail tunnel was inadequate.
A private email released to Radio New Zealand under the Official Information Act reveals the Ministry of Business, Innovation & Employment criticised the company's handling of the incident in the Kaimai Tunnel in August.
Ten contractors in the tunnel did not leave straight away when their gas alarms went off, due to insufficient training.
The internal email between senior ministry managers says KiwiRail focused its investigation and recommendations on what it calls 'soft' mitigation control measures.
KiwiRail suggested improvements to training and new rules on how workers should behave in an emergency situation but did not look at how it could make the tunnel itself a safer environment for them.
The railway company has admitted mistakes were made and has since reviewed its procedures.
The lawyer representing the Rail and Maritime Transport Union, Hazel Armstrong, is calling for a new investigation.