The death toll today climbed to 50, as anxious Muslim relatives waited to bury their loved ones, two days after the worst terror attack in the country's history at the Al Noor mosque in central Christchurch and another in the suburb of Linwood.
Dozens of other people have been injured.
Islamic law calls for bodies to be cleansed and buried as soon as possible after death, usually within 24 hours.
At a news conference this afternoon, Arden confirmed that only some bodies were being returned.
Earlier in the day, Police Commissioner Mike Bush said police were working with pathologists and coroners to release the bodies as soon as they could.
"We have to be absolutely clear on the cause of death and confirm their identity before that can happen. But we are so aware of the cultural and religious needs. So we are doing that as quickly and as sensitively as possible."
Police have released a preliminary list of the victims to families, which has helped give closure to some relatives who were waiting for any news.
The scale of the tragedy and the task still ahead became clear as supporters arrived from across the country to help with the burial rituals in Christchurch and authorities sent in backhoes to dig new graves in a Muslim burial area that was newly fenced off and blocked from view with white netting.
The suspect in the shootings, white supremacist Brenton Harrison Tarrant (28), an Australian who was living in Dunedin, appeared in court yesterday amid strict security, shackled and wearing all-white prison garb.
He showed no emotion when the judge read him one murder charge. More charges were likely.
Bush said at a news conference today that they found another body at Al Noor mosque as they finished removing the victims, bringing the number of people killed there to 42.
Another seven people were killed at the Linwood mosque and one more person died later at Christchurch Hospital.
Another 34 victims remained at Christchurch Hospital, where officials said 12 were in critical condition. And a young child who was in a children's hospital in Auckland was also listed as critical.
Dozens of Muslim supporters gathered at a centre set up for victims, families and friends across the road from the hospital, where many had flown in from around New Zealand to offer support.
About two dozen men received instructions on their duties this morning, which included Muslim burial customs.
Abdul Hakim (56) of Auckland, was among many who had flown in to help.
"As soon as people die we must bury them as soon as possible," Hakim said. "We are all here to help them in washing the body, putting them in the grave."
Javed Dadabhai, who flew from Auckland after learning about the death of his 35-year-old cousin Junaid Mortara, said the Muslim community was being patient.
"The family understands that it's a crime scene. It's going to be a criminal charge against the guy who's done this, so they need to be pretty thorough," he said.
Still, it was hard, he said, because the grieving process wouldn't really begin until he could bury his cousin.
People across New Zealand were still trying to come to terms with the massacre that Prime Minister Jacinda Ardern described as "one of New Zealand's darkest days."
A steady stream of mourners arrived at a makeshift memorial outside the Al Noor mosque, where hundreds of flowers lay piled amid candles, balloons and notes of grief and love. As a light rain fell, people clutched each other and wept quietly.
Under a nearby tree, someone had left a potted plant adorned with cut out red paper hearts. "We wish we knew your name to write upon your heart. We wish we knew your favorite song, what makes you smile, what makes you cry. We made a heart for you. 50 hearts for 50 lives."
Tarrant, the suspect, had posted a jumbled 74-page anti-immigrant manifesto online before the attacks and apparently used a helmet-mounted camera to broadcast live video of the attacks.
The gunman livestreamed 17 minutes of the rampage at the Al Noor mosque, where he sprayed worshippers with bullets. Facebook, Twitter and Google scrambled to take down the video, which was widely available on social media for hours after the bloodbath.
Ardern said Tarrant was a licensed gun owner who bought the five guns used in the crimes legally.
"I can tell you one thing right now, our gun laws will change," Ardern said.
She did not offer too much detail, but said a ban on semi-automatic weapons would be looked at. Neighbouring Australia has virtually banned semi-automatic rifles from private ownership since a lone gunman killed 35 people with assault rifles in 1996.
Before Friday's attack, New Zealand's deadliest shooting in modern history took place in 1990 in the small settlement of Aramoana, near Dunedin, where a gunman killed 13 people following a dispute with a neighbour.
