First results cleared the woman - widely reported to be Gore nurse Bronni McBain - of the disease yesterday. However, a second test was required to confirm the result, Health Minister Dr Jonathan Coleman said.
''We should have the results of the second test within 48 hours,'' he said yesterday.
''It is highly unlikely that it will come back with a positive result.''
Mrs McBain recently returned from Sierra Leone, where she was caring for those suffering from the untreatable virus.
The only person to come into contact with Mrs McBain during the infectious period was her husband, Gary, who was self-monitoring as a precaution.
Neighbours of the McBains in Ruia St, Gore, were woken by sound of a helicopter arriving early on Saturday morning.
Mrs McBain walked to the helicopter and was transported to Christchurch Hospital in a specialist iso-pod patient transfer unit accompanied by health care workers in protective suits.
Dr Coleman said Mrs McBain was in a stable condition in the hospital.
''The patient ... will remain in one of Christchurch Hospital's dedicated specialist medical isolation rooms until the result of the second test is known,'' he said.
''I would like to acknowledge the efforts of the patient and their family, who carefully followed the protocols for returning health workers, to ensure that there was no potential risk of others being exposed.
''The health sector has planned for months for just such an eventuality, and it is pleasing to see that all the preparation has paid off.''
A neighbour, who wished to remain anonymous, said his family was woken by the helicopter landing in the street.
The house remained ''pretty quiet'' during the weekend.
He had no concerns about the potential scare and was impressed by Mrs McBain's work.
''She must be pretty awesome to want to go over there and want to do that work,'' he said.
Another neighbour said ''everybody is definitely impressed'' by the nurse's selfless spirit.
Mrs McBain, who was contacted by the Otago Daily Times on Friday but said she was not the nurse involved, left Sierra Leone on March 8.
She previously helped in a tsunami-ravaged region of Sumatra in 2005 and spent time nursing in Vanuatu in 2004 at her own cost.
Attempts to contact the McBain family and friends were unsuccessful yesterday.
Mrs McBain was recognised at the inaugural Southland Nursing Excellence Awards in 2008.
Her daughter works as a nurse at Dunedin Hospital.
