A landslide came crashing down on popular Coromandel beach Cathedral Cove, with witnesses describing the moment as "frightening" and "scary".
Between 9.30am and 10am today, rubble, boulders, rocks, trees and debris came sliding down the cliff face, pounding on to the sand and water below.
The Department of Conservation (DOC) has now closed the beach for at least a week.
Chris Southwick, who witnessed the landslide, told the Herald he could hear a "massive boom", adding it could have been catastrophic if tourists had been sunbathing on the beach.
"It was a massive boom when it came down. We called the coastguard to report," he said.
"Lucky there was nobody on the beach at that time. The tree under it was used by many for shelter. If it was peak time there would have been many people there. Very lucky it didn't kill anybody."
He estimated there would have been at least a few hundred tonnes of weight behind the landslide.
DOC operations manager Nick Kelly said with visitor safety the priority, the path to the idyllic beach has been blocked to prevent access.
"Cathedral Cove is prone to rockfall and erosion during and after weather events like the ones we've seen over the last month," he said.
"We consistently monitor the geology at the site, and we are concerned the large landslip that has occurred in the last 24 hours signals a greater chance of more erosion there.
"The slip is active with more material falling to the beach."
With Cyclone Gabrielle predicted to hit the North Island next week, potentially packing heavy rain and gale-force winds, Cathedral Cove will be closed for at least a week and possibly longer, DOC confirmed. There is no reopening target date at this point.
"This is not a decision we've taken lightly," Kelly said. "We appreciate how popular Cathedral Cove is with visitors and our community, but the risk of landslide, combined with more wild weather, leaves us with no choice."
Kelly said DOC was arranging for geotechnical engineers to visit and assess the site - but that work will take time to arrange and undertake.
Commercial operators who take visitors to Cathedral Cove have been asked not to land on the beach until further notice. Boaties can still enjoy the Te Whanganui a Hei Marine Reserve around the cove and are urged to exercise caution and be up to date with weather forecasts and expected high sea swells.
"Our message here is simple: stay away from Cathedral Cove for your own safety," Kelly said.
DOC confirmed last month the popular tourist spot had been closed to visitors in early January, with the organisation "strongly discouraging people from visiting" due to the weather.
Just last month Cathedral Cove was closed to visitors due to the subtropical storm that battered the Coromandel.
* This story was first published on the New Zealand Herald website.