"The helicopters and crews are making the most of the cooler conditions to knock out the remaining hot spots and mop up the fire," Fire and Emergency NZ said.
"Small hot spots may continue to be visible over the next few days. Operations on the fire ground will ramp up around 8am and continue throughout the day."
Fenz's operational support team from Remutaka told people to avoid the area if possible.
The blaze was under control around 5pm last night but was still about 2ha in size.
It flared up not long after, and some locals were told to be ready to evacuate as a precaution.
The fire had been re-mapped this morning and while it did not grow significantly overnight it had burnt through more vegetation following a flare-up just after 6pm, Fenz said.
"Residents of Trentham and Silverstream will notice smoke still in the area this morning. Smoke may also continue to be visible over the next few days.
"If you are affected by the smoke, particularly those downwind of the fire, please keep your windows and doors closed."
Anyone who needed medical advice should call Healthline on 0800 611 116, Fenz said.
The fire was first reported after 3pm on Saturday.
It had been brought under control before sunset, after three helicopters were brought in to drop water on it from above.
Silverstream residents were yesterday told to conserve water in their houses as the reservoir filled back up. It had been depleted by fire crews using the water to fight the fire.
Helicopters were continuing operations until 8.30pm last night and ground crews were to be scaled back around 9.30pm.
About 10 nearby properties had been asked to prepare to evacuate if required "as a precaution".
"Fire and Emergency has been in contact with these properties. People are asked to please stay away from the area and let the firefighters do their work," Fenz said.
It's one of several large fires that have been sparked in recent days in tinder-dry spots around New Zealand. Niwa has said some regions are heading for drought conditions for the third year in a row.
A large blaze near a wastewater treatment plant in Taupō last night also prompted evacuations.
At least eight fire trucks and one helicopter attended the vegetation fire yesterday on Rickit St, Taupō.
Precautionary evacuations were made but there were no structures involved.
A fire crew stayed to monitor the fire scene overnight with fresh crews arriving this morning to put out any areas that were still burning, FENZ said.
Police were asking the public to avoid the Rickit St area of Taupō, near the wastewater treatment plant and cemetery, while emergency services responded.