Terrifying bridge collapse caused by 'highly unusual manufacturing defect' in chain

The Department of Conservation says a batch of high tensile chain that caused the collapse of a walking bridge on Lake Waikaremoana, plunging four French tourists into the river below, was not used in any other bridges.

Shocking video has emerged of the moment the tourists fell eight metres from the Hopuruahine Bridge at the end of their multi-day tramp along Lake Waikaremoana last month.

The tourists had some minor cuts and bruises but were not seriously hurt.

DOC confirmed last month a cable broke as the party crossed the bridge.

Today, Deputy Director General Operations Mike Slater says independent engineering investigations have identified that the failure was caused by a highly unusual manufacturing defect in a link of a specific batch of high tensile chain used for the Hopuruahine Bridge’s construction.

DOC has checked its bridge network and this specific batch of high tensile chain was not used in any other bridges, Mr Slater says.

"We are continuing to review our response but DOC remains confident in the safety of its bridge network," he says.

"DOC has a rigorous system for inspecting and testing our bridges and this is the best practical way to maintain the safety of our structures." 

The department has briefed the French trampers on the findings of the bridge investigation.

The video filmed by one of the tourists and posted on YouTube shows the tourists walking along the bridge before the structure gives way and the party plunges into the river.

The Lake Waikaremoana Track is one of New Zealand's heavily marketed nine Great Walks.

The 46-kilometre tramp takes between three and four days to complete and features views from Panekire Bluff along with the Korokoro Falls.

The park is jointly run by DOC and Tuhoe and is still open to the public.