These involved the use of a synthesised voice, with calls occurring at a similar time and day of the week.
Read more: Bomb threat at Broofield School
At least three of the schools called today had received calls previously.
Police said they were undertaking a number of lines of inquiries to establish the exact origin of these calls, and are continuing to work with the Ministry of Education and individual schools to gather information and ensure the safety of staff and students.
Similar incidents have occurred overseas in United States, and more recently Australia.
Until police can rule out any actual threat, police said they would take all such calls seriously and respond accordingly.
"How a school responds to these calls is a matter for the schools' management in conjunction with police.
"Schools will respond differently according to their individual circumstances and the information available to them," the police statement said.
Police would not disclose the names of each school who received a call today given the ongoing investigation and in the interest of preventing further such calls being made to other schools.