The Navy is investigating an alleged breach of Auckland's boundary by a junior sailor last weekend.
The fully vaccinated sailor reportedly travelled to attend the funeral of a close family member but had not applied for a Ministry of Health travel exemption.
"The sailor has been instructed to isolate in their rural property in Hawke's Bay and get a Covid test," the NZDF says.
"The RNZN is investigating the alleged border breach and the surrounding circumstances. The regional health authority has been informed."
The Deputy Chief of Navy, Commodore Melissa Ross, said: "An investigation is currently under way into how the sailor managed to cross the border without an MoH exemption or essential travel status.