"Fortunately other than some scratches and a little bit of bruising, they are not seriously injured. That's a very fortunate outcome."
Mr Slater said a full investigation was now underway to work out what had occurred.
"We've got a very comprehensive and robust asset management system."
He said this included an inspection programme.
"Those bridges every six years are inspected by an engineer who would give a full engineering inspection. Every second year between that time they would be inspected by a qualified departmental inspector and every 12 years they undertake a full load testing."
The bridge was last inspected in September last year, and was fully inspected by an engineer 18 months ago, Mr Slater said.
"An event such as this is extremely rare occurrence and we just need to understand in this particular case exactly what did happen."
The bridge was now closed, Mr Slater said.
An engineer was currently on-site and would carry out an engineering inspection to understand what failed in terms of the bridge's construction.
"We will also look to undertake an investigation so we understand the detail of our management regime over time including those inspection programmes."
Labour's Conservation spokesperson Ruth Dyson said the Government must act urgently and decisively to assure trampers on all Great Walks that every bridge will be checked as soon as possible for safety.
"It is a huge relief the four overseas tourists on the Lake Waikaremoana bridge that failed yesterday landed in water and were uninjured. This is good luck not good management. Our reputation cannot rely on luck.
"The cable failure is not only extremely concerning, it leaves New Zealand vulnerable to harmful tourism reaction. This must be sorted immediately.
"Additional resources must be given to the Department to carry out this work as it is obvious the pressures on them following seven years of budget cuts, are causing greater strain than they can tolerate."
"Different scenario to Cave Creek"
Yesterday's incident comes 20 years after the death of 14 people at Cave Creek.
Thirteen outdoor education students and a DoC officer died when a poorly constructed DoC viewing platform gave way in the Paparoa National Park on the West Coast in April 1995.
A Commission of Inquiry later attributed the disaster to systemic failures at DoC, which led to a poorly constructed viewing platform.Mr Slater said yesterday's incident was "quite a different scenario".
"Post-Cave Creek was when we actually looked to put in place a very comprehensive and robust asset management approach, that has both very clear standards for construction, clear inspection programmes, clear maintenance programmes and so we have all of those in place and therefore we do not anticipate a situation such as we might have had in Cave Creek."
The Lake Waikaremoana Track, in the Te Urewera National Park in the central North Island, is one of DoC's nine Great Walks.
The three- to four-day tramp follows roughly half of the lake's circumference and is a popular holiday destination.
