Marlborough fire crews are focusing on areas around homes as they continue to work through hotspots in Onamalutu Valley.

Over 600 hectares was decimated in the firestorm which erupted late last Wednesday.

Principal Rural Fire Officer Richard MacNamara says they have now stabilised the 16 kilometres of the fire boundary.

He says it will be a long time before they start to scale back the operation.

"The fire is not dead by any stretch of the imagination internally. That's going to take two-to-three weeks and in fact it probably won't be declared out until we get two-to-three inches of rain and God help us, I can't see when that's coming."