Civil Defence has cancelled the official threat warning from Mt Tongariro.
It says the mountain's activity since it erupted on Monday night has subsided, and no ash is now being produced; nor have there been any lahars or lava flows.
Civil Defence says the volcanic alert level remains at level 2 (the highest level is 5) and Tongariro could erupt again with little or no warning.
But it says the immediate threat warning has been cancelled.
Air New Zealand, meanwhile, says it is restarting flights at most North Island airports as the ash cloud from the eruption begins to clear.
About 40 flights were cancelled on Tuesday morning but the airline says the ash cloud is clearing to the east of Tongariro, and it is resuming services to Gisborne, Rotorua, Taupo and Palmerston North.
It says flights to and from Napier are still being delayed or cancelled.
The Desert Road and nearby State Highway 46 from Rangipo to National Park have reopened after being closed for several hours as a precaution.
Some people living near the volcano have chosen to leave their homes, but Civil Defence has not ordered any evacuations.
Civil Aviation's manager of meteorology, Peter Lechner, told Morning Report that the ash cloud was expected to reach as far as Gisborne to the north and northern Wairarapa to the south.
Ash falls inland from Napier
People in affected areas are advised to stay indoors but protect themselves from the ash if they go outside, because it is a health hazard, especially for those with breathing difficulties.
Civil Defence in Hawke's Bay is warning residents to beware of ash even if the skies appear clear.
At mid-morning on Tuesday it said that about 1mm of ash had fallen inland from Napier and there was a strong smell of sulphur.
Civil Defence says so long as ash is not visibly falling it is safe to go outside, but fine ash could cause problems for people with breathing difficulties.
Residents are being asked to prepare for potential power outages.
The Manawatu-Whanganui Regional Council is advising residents living downwind of the eruption to disconnect their rainwater tanks to prevent ash contaminating the water.
Ruapehu skifields unaffected
The skifields at Mt Ruapehu are unaffected: the general manager of the Turoa and Whakapapa fields, Dave Mazey, says the wind is taking the ash cloud away from the fields.
Federated Farmers says ash fall has had minimal impact on pastures and stock drinking water. It says the ash appears mainly to be falling away from farms and onto forested areas and Tongariro National Park.
The president of Rotorua/Taupo Federated Farmers, Neil Heather, says if there is another eruption with a heavy fall of ash, farmers should prevent their stock from eating ash-covered grass.
Army training continues
Training around the Waiouru Military camp is continuing, despite the eruption.
The Army says it had a number of people in the area when it happened, and evacuated them as a precaution. It subsequently did a risk assessment, and the same soldiers have been allowed to continue with their training.
Police say teams dropped by helicopter onto the mountain found the Ketetahi hut empty, but three people from another hut.
Local iwi say 24 people left the area of Mount Tongariro after the eruption. At a news conference on Tuesday, Ngati Tuwharetoa representative Bubs Smith said the priority was to get older and younger people, as well as those with respiratory problems, to a marae in Turangi.
MetService says it expects the clouds of ash to linger around the central North Island until late on Tuesday night, when a rain-bearing westerly front should help to disperse them.
North Island prisons unaffected
The Department of Corrections says the eruption has not caused any health problems for inmates or staff in the area.
It has assessed all six prisons in the central North Island, and there has also been no damage to property.
All facilities have returned to normal operations, except for the closest - Tongariro/Rangipo Prison - which is operating on weekend routines.
Corrections has set up a phone line for families of prisoners to call if they are worried. The number to call is 04-460-3000.