Police also arrested an 18-year-old man, but his involvement was reportedly "tangential".
Police said two other people were in custody.
"We represent diversity and compassion, a home for those who share our values, a refuge for those who need it. So we are doing that as quickly and sensitively as possible".
The alleged gunman has been identified by authorities as Brenton Harrison Tarrant, a 28-year-old native of Grafton, Australia.More news: Donald Trump Jr comes to Chelsea Clinton’s defence over NZ massacre remarks
The death toll rose to 50 victims after investigators found another body in the mosque, said New Zealand Police Commissioner Mike Bush. "Hatred always is. I'm not going to give airtime to the motives disposed by this cowardly person who has attacked a vulnerable community in their time of worship", Dalziel said.
At least one victim was expected to be returned tonight, he said, and emphasised that "the most important thing is to ensure that identifications are done to 100 per cent certainty".
Thirty-four people were in Christchurch Hospital, with 12 in intensive care, while a child was moved to a children's hospital in Auckland.
Kensington Palace has released a statement on behalf of Meghan Markle, Prince Harry, Prince William, and Kate Middleton in response to the New Zealand terror attack. About two dozen men received instructions on their duties Sunday morning, which included Muslim burial customs.
He said up to 70 people were praying inside Linwood when gunshots were heard. "We are all here to help them in washing the body, putting them in the grave". He was likely to face further charges, police said.More news: Lawyer: US Navy Veteran Held in Iran Sentenced to 10 Years
Still, it was hard, he said, because the grieving process wouldn't really begin until he could bury his cousin.
The atrocities took place in Masjid Al Noor mosque, where at least 41 people were killed and another seven were shot dead inside the suburban Linwood Masjid Mosque. As a light rain fell, people clutched each other and wept quietly. We wish this did not happen. We wish we knew your favorite song, what makes you smile, what makes you cry.
Video footage widely circulated on social media, apparently taken by a gunman and posted online live as the attack unfolded, showed him driving to one mosque, entering it and shooting randomly at people inside. Facebook said it had removed 1.5 million videos of the attack in the first 24 hours, and it was also removing all edited versions, even those without graphic content. The two mosques were full as the attacks occurred just after Friday prayers had started.
Ardern said Tarrant was a licensed gun owner who allegedly used five weapons, including two semi-automatic weapons and two shotguns, which had been modified.
Ms Ardern confirmed her office was one of about 30 that had been sent the manifesto nine minutes before last Friday's massacre, but it did not contain details of where the attacks would take place. He was hoping semi-automatics were not banned, but he and his shooting friends were buying the weapons, which can cost anything from NZ$600 (US$400) upwards.More news: Facebook says it 'quickly' removed New Zealand shooter's video