Police Commissioner Mike Bush says the criminal investigation into the Christchurch terror attacks is the largest one ever ever undertaken by New Zealand police.
Mr Bush has just given the latest update on the Christchurch terror attacks.
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He said there were 250 specialists and investigators working on the case in New Zealand, with the FBI and Australian authorities also helping with this case.
Information from the investigations in New South Wales was being shared with authorities here.
"We believe there was only one attacker responsible for this horrendous event."
He said other people may be in support of the attacker and this is a very important part of this situation.
"I think the public really need to know that we believe definitively that there is only one person.
"We have a very comprehensive and wide reaching investigation. We'll reach into every corner to ensure there are no more threats."
Mr Bush said the threat level remained high and there would continue to be an increased police presence around the country. The public are once again urged to speak up if they see anything suspicious.
"If you see something, say something, don't second guess it. If you're worried, we'll be there."
Threats that come to the attention of the police are followed up, he said.
"Whatever arises will be dealt with, will be met."
He said police stood ready if anyone would like to give over firearms to them.
Most front line officers across the country will be carrying firearms as a precaution at the moment. Those that aren't carrying have immediate access to them.
Fifty people have died in the shootings at Al Noor and Linwood Mosques and a further 50 are injured.
Police have told reporters in Christchurch that they aim to have all mosques in the city open by Friday.
Mosques in the city have been closed since the attacks on Friday.
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