Heavy rain caused the massive slip at Beachside Holiday Park, nestled at the foot of Mount Maunganui, as a summer storm swept down the North Island on Thursday.
Those missing ranged in age from 15 to 71 and included a Swedish tourist and a teenager originally from Italy.
Work to find the missing was suspended at the weekend because of fears the ground remained unstable.
The search resumed on Monday as authorities said the recovery teams were working in dangerous conditions.
"We're just holding out for the weather to improve because moisture is the enemy at this point," police Superintendent Tim Anderson said in a statement.
"The ground is saturated and what we need is days of fine weather."
A wave of mud from the mountain hit the campsite, which is in a picturesque beachside spot named after an extinct volcano. Images showed vehicles, travel trailers and an amenities block crushed by debris.
On Thursday, rescuers said they had heard voices beneath the rubble but by Saturday, authorities said they didn't believe any of those missing had survived.
They have been named as Lisa Anne Maclennan, 50; Måns Loke Bernhardsson, 20; Jacqualine Suzanne Wheeler, 71; Susan Doreen Knowles, 71; Sharon Maccanico, 15; and Max Furse-Kee, 15.
The horror unfolded at the beachside campsite during New Zealand's peak summer holiday period.
Parts of the North Island recorded record rainfall during the deluge including the city of Tauranga, where Mount Maunganui is located, which registered its wettest 24-hour period since 1910.
Along with the six missing at the campsite, the storm killed three others.
Also on Thursday, two people were killed when a landslide buried a house in nearby Papamoa.
A day earlier, a 47-year-old man from Kiribati was swept away by floodwaters while driving in New Zealand's far north. His body was found on Saturday.
The unusually wet weather prompted questions about whether evacuation orders should have been given before the campsite tragedy.
The fire service said on Monday it had delivered a warning from a member of the public about a slip near the holiday park to the local Tauranga City Council, the landowner of the site, four hours before the fatal landslide.
The council said it would hold an independent inquiry into the episode.
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