Wellington Police are now aware of 16 suspicious letters inferred to contain 1080 poison being sent to local body, central government agency and private business addresses.
Detective Senior Sergeant Paul Borrell, Wellington CIB, said four letters were mailed to Greymouth and West Coast addresses and were received in recent days.
"They appear to be similar to four received in Wellington and eight in the Nelson area last week," he said.
"Inquiries, including forensic examinations are continuing."
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