Deputy Director General Operations Mike Slater says laboratory analysis conducted at the University of Canterbury School of Engineering has revealed manufacturing defects, known as quench cracks and embrittlement, in a section of 24 millimetre diameter high tensile chain used on the bridge.
Mike Slater says there were no previous indications of weakness with the chain used on the Hopuruahine Bridge and this type of sudden link failure is highly unusual.
Mike Slater says DOC is seeking confirmation of the defects through a second round of specialist testing.
Mike Slater says the specific batch of chain found on the Hopurahine Bridge was not used in the construction of the other nine smaller bridges on the Lake Waikaremoana Great Walk and they have all passed detailed engineering inspections.
He says checks have not revealed any sections of this batch of chain being used in DOC's other suspension bridges around the country.
Mike Slater says DOC has kept Te Urewera Board fully updated on the bridge investigations.
He says DOC and Tuhoe are working with the trampers involved in the incident to ensure they are also briefed on the findings.
Mike Slater says DOC will be installing new cable strops on the Hopuruahine Bridge over coming weeks and will be working with Tuhoe to recommission the structure after fresh load testing is completed.