Civil Defence says a lake formed by a landslide is still at risk of breaching at Goose Bay near Kaikōura.
Seventeen people from 35 Goose Bay homes were evacuated on Wednesday after a dam of water formed by a land slip was discovered upstream.
Kaikōura Civil Defence controller Murray Sinclair said geotechnical engineers were doing modelling scenarios for what would happen if the dam breached.
Mr Sinclair said residents could be evacuated for 10 days.
He said the pool of water was 200 to 300 metres long, 10m wide and up to 10m deep.
Residents were told to stay with family, friends or at the Recovery Assessment Centre in Kaikōura.