However the Herald can reveal that police were not called until about 10.10pm.
The pair have since been described as "dangerous" and a significant effort is underway to bring them back into custody.
Prime Minister Jacinda Ardern said she was concerned by the fact a teenaged murder was able to escape from custody.
Officials are looking into how that happened, she said.
Stabbing victim left to die
In February last year Hanara - who was only just 15 - was jailed for life with a minimum non parole period of 10 years for murdering Kelly Donner, 40.
A High Court jury heard how Hanara stabbed Donner four times with a knife - twice in the neck and once in the chest and another time in the shoulder - on March 4, 2018.
One of the blows proved fatal, severing the 40-year-old's carotid artery and leaving him dying, alone, in a pool of his own blood.
Due to his age he was remanded in the Youth Justice facility.
Police made the escape public last night - about an hour after the Herald sought details from Oranga Tamariki.
Both organisations are justifying the almost 24-hour delay in alerting the public to the escape of the dangerous youths.
However in a statement OT deputy chief executive of youth justice services Allan Boreham said he was "very concerned" by the escape.
"We continue to assist police in efforts to locate them," he said.
"Initial inquiries indicate the teenagers broke out through a reinforced window, before escaping across a roof and through the staff car park.
"Staff became aware of the escape at 9.30pm.
"We are still investigating the timing and details but can confirm our staff searched the perimeter and called the police when the teenagers could not be found."
The Herald understands that when police were alerted officers re-searched the grounds at the facility and Fire and Emergency New Zealand staff were brought in to help look on the rooftops as the Eagle helicopter was not available.
A source said the incident was captured on CCTV and the teens could be seen getting across the roof and scarpering into the night.
Boreham said neither teen had ever escaped from a youth justice residence in the past - however Ratuhad previously absconded from a community-based placement.
"We were already working with the police when we received the first media enquiry and the family of Haami Hanara's victim was notified by police before the escape was made public," he said.
"All decisions on public safety alerts are made by the police."
Detective Senior Sergeant Albie Alexander said once police were notified of the escape "a number of inquiries were initiated".
"There are a number of inquiries police have to make and a decision around publicising information needs to be made in the best interests of the investigation as often publicity can hinder operations," he said.
"However we are now at a point where we are seeking the public's assistance and want to reassure our communities that every effort is being made to locate these individuals."
Alexander said the hunt for the pair was "ongoing across a number of policing districts".
"And will remain in place until we locate Hanara," he said.
"Anyone who may be assisting Hanara in evading police are warned that they could face criminal charges themselves.
"My message to Hanara is to do the right thing and hand yourself in to the nearest police station."
Alexander confirmed Hanara was considered a dangerous offender.
"We are continuing to urge anyone who may encounter Hanara to not approach him and instead call 111 immediately," he said.
Boreham said Oranga Tamariki would be looking at how the escape happened.
"Hundreds of teenagers spend time at our youth justice facilities every year," he said.
"Our focus is on understanding how these young people were able to escape as we don't want this to happen again."
Korowai Manaaki Youth Justice Residence has beds available for young people who have active or proven charges in the courts - including those convicted in the District or High Court who due to their vulnerability are considered "better managed" in a residence as opposed to prison.
Boreham said each young person is assessed by a team of professionals to ensure the residence is the most suitable place for both them and the community.
In very rare cases it is determined that a Corrections facility is better suited to manage the young person involved.
That determination is made by way of a joint assessment by both Corrections and Oranga Tamariki and examines the risk posed to other young people, staff, self and risk of violence.
A young person remanded in custody can also be held in a prison if a Judge makes an order under the Oranga Tamariki Act.
The number held in a Corrections facility is so low that we can't provide more information because of the risk of identifying the young people.
A young person is defined by age and is any person under the age of 18 years old.
