Speaking at a press conference on Sunday following the attacks that killed 50 people, Ms Ardern said if her office could have done anything with the information sent by accused shooter Brenton Tarrant, "absolutely we would have".
Mr Bush said four other people arrested during Friday's police operation have either been released or charged with "tangential" offences.
Twelve operating theatres worked through the night on the more than 40 people wounded, said hospital authorities.
"At just that moment, there was one young guy who usually takes care of the mosque and helps with parking and other stuff, so (the man) saw an opportunity and he pounced over to him and grabbed his gun".
On Friday, March 15, 50 people were killed and 20 more were injured in a mass shooting that took place in two mosques in the Soth Island city of Christchurch.
In a statement posted online, Sunday, police said officers were continuing to work "closely and extensively with partners to identify the injured and deceased victims of the Christchurch attack".
"The magnitude of this is the thing that is the most significant issue for people". Police believe that Tarrant single-handedly carried out the terror attack at both the mosques during the ongoing Friday prayers for which a large number of people had congregated.
Pool via Getty Images Brenton Tarrant, charged in relation to the Christchurch massacre, is escorted in the courtroom Saturday in Christchurch, New Zealand.
Pakistan's high commissioner said six citizens had been killed and three were missing.
For nearly 3 days forensics teams have been working through multiple crime scenes - at the Al Noor and Linwood mosques as well as a house in Dunedin, the southeastern city where the Tarrant lived.
Ardern added that the mail was transferred to the security services within two minutes after it was received.
Tarrant's sister and mother, who still live in the area, have been placed under police guard and even family members can't contact them, she said.
The shootings have raised new questions about violence being disseminated online.
But despite the horror of the Christchurch shootings, some local residents who AFP spoke with Saturday warned against any drastic moves on gun control.
Ardern has vowed to change the country's gun laws and to uncover how a self-avowed extremist legally purchased two semi-automatic weapons, reportedly AR-15s, two shotguns and a lever-action gun without drawing the attention of the authorities. "Our gun laws will change".
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