Further organisations have received threats by email today, following yesterday's messages which affected over a dozen around the country.
Police said to date more than 70 organisations have received concerning emails, including schools, hospitals, courthouses and places of worship.
"We know that these emails are causing real concern among members of our community, particularly the emails directed at places of worship," police said.
"Police remain confident that the emails being received are from the same source, and are not targeted at any particular community or group."
A number of schools in North Auckland have been affected.
On its website, Browns Bay School wrote: "School closed due to bomb threat, please stay home and offsite."
Other schools in the North Auckland area also said they have received a bomb threat.
Stanmore Bay School (primary) said the school is closed due to "health and safety reasons".
"Those currently on site are safe and with staff. We will have an update for you soon. Our gates will remain closed."
Orewa College is also closed for the day, and is asking parents to "follow your family emergency plan".
Post Primary Teachers Association (PPTA) acting president Chris Abercrombie said it was "incredibly disruptive that these threats are occurring" but schools do have "processes to deal with them".
"Their primary concern will be ensuring the safety and wellbeing of staff and students," he said.
Yesterday, police said there was no danger from the threats which targeted 15 organisations, including schools and hospitals.
Te Whatu Ora national director hospital and specialist services Fionnagh Dougan told 1News yesterday some of its hospital sites received an "email of concern", which was then referred to police.
"Staff have followed police advice and we are remaining vigilant. Our hospital sites have remained open and all services are continuing," she said.
St Kentigern College in Auckland's Pakuranga sent students home as a precautionary measure around 11.30am after receiving a threat.
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