Some parents whose children attend a primary school in Canterbury have been receiving threatening letters over the past week, prompting police to conduct an investigation into the matter.
Police said they had received reports that two families, both with children at Mt Pleasant School, in Mt Pleasant, Christchurch, had received letters demanding money, and threatening harm to children in the last week.
Detective Inspector Greg Murton said police were working closely with the families involved, as well as Mount Pleasant School, to investigate the matter further.
"Police are treating this matter very seriously and we have a team of detectives working to identify the author of these letters.
"We have increased police patrols in the area and also put additional security in place for the families involved.