Engineers from the Manukau City Council are keeping a watch on a slip that led to six houses being evacuated in the settlement of Kawakawa Bay.
They fear the entire hillside will collapse within four days, and cover the coast road and the foreshore with tonnes of mud and rocks.
The council on Friday blocked vehicle access to the area and removed workmen from the site for their own safety.
It also expressed concern about people walking along the foreshore road despite warnings to stay away.
The council says the hillside looks deceptively calm but is very unstable.
Heavy rain has closed the main road to the village since Sunday, forcing about 1500 people to use a longer, alternative route.
The council expects the road to be closed for up to a month.
The slip is described as the size of a shopping mall and the council says it's impossible to know when the hillside might collapse.
A temporary ferry service for commuters to Auckland city starts on Monday.