A Dunedin police officer examines the letter box of New Zealand First's South Dunedin electorate office on Saturday where a live shotgun shell was posted through the letter flap. Photo by Jane Dawber.
Police were called to the Hillside Rd office about 9am when a staff member retrieved the mail, to find a live 12-gauge shotgun shell in the box.
Senior Sergeant Craig Brown said it was believed the cartridge might have been placed in the box some time between Wednesday night and Saturday morning.
Police were were investigating, he said.
"It's always serious when you've got firearms and ammunition involved."
The party's Dunedin South candidate is Randall Ratana. He was unable to be contacted last night.
A spokesman said party officials were leaving the incident for the police to handle and had no comment to make.
