Civil Defence says at least least 100 flood-affected families in Nelson and Tasman will not be allowed back into their homes in time for Christmas.
Of the homes with red stickers, 93 have now been reassessed as still unsafe to enter, or fit only for emergency entry following the record floods and slips last week.
Engineers are allowing 12 homeowners to return to their houses after the second assessment in as many days.
But 44 houses are still too dangerous, and 49 more have yellow stickers, meaning restricted entry only and no habitation.
With 34 more homes still to be reassessed, the number unable to return home is expected to climb to well over 100.
Civil Defence controller Alec Louverdis says Nelson's main water pipeline appears safe, after repairs to prevent a possible breakage due to slips beneath it.
The waterfront route into Nelson, Rocks Road (State Highway 6), will re-open some time on Friday, after round-the-clock work to avert the danger of more slips, officials say.
Boil water notice for Richmond
Residents in Richmond are advised to boil all drinking water as a precautionary measure.
The notice was issued on Tuesday after Nelson-Tasman Civil Defence managers received results of water tests from the urban supply's Lower Queen St wellfield.
Spokesperson Chris Choat says the wellfield was flooded in last week's storm and could have been contaminated. The amount of water quality tests undertaken by Tasman District Council staff meant the notice was not released earlier.
Mr Choat says the boil water notice is likely to be lifted by Christmas.
Water should be boiled for drinking, cleaning teeth, food preparation, washing utensils, making ice and for pets.