More than 300 hives will be destroyed at a property in Narrabri following the identification of the Varroa mite on Monday, and more could come.

The majority of the hives had already been euthanised but due to wet weather a small number have yet to be destroyed.

A spokesperson for the Department of Primary Industries (DPI) said reimbursement to affected bee keepers was currently under negotiation.

The detection, which was linked to the outbreak in Newcastle, has resulted in a 25km surveillance zone being established around the property, where officials will monitor and inspect feral honey bees.

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Thousands of bee hives were inspected across Tamworth and the NSW North West following the detection on Monday.

As of Thursday, more than 15 million bees across the state had been euthanised and 1533 hives had been destroyed across 31 infected premises.

With each hive containing anywhere between 10,000 to 30,000 bees it is possible that up to 45 million bees have been euthanised since the mite was first detected on June 22.

But despite the growing numbers, authorities are confident they can contain the outbreak.

NSW Agriculture Minister Dugald Saunders said the number of bees that had been affected was "significant".

He said one of his main concerns was about keeping people in the industry as the trying time takes a toll.

"[Bees] do breed up again very quickly but it's about making sure you've got all of the people still wanting to stay in the industry after it's been decimated like this," he said.

Acting chief executive of the Australian Honey Bee Industry council Danny Le Feuvre said it's heartbreaking for those impacted.

"It's certainly devastating for the people involved ... particularly the beekeepers who have spent alot of time and effort in building their businesses and building their hives up...and tending to them," Mr Le Feuvre said.

- with AAP

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