A fire at an egg-laying farm in the Waikato has claimed the lives of 50,000 hens.

The figure was earlier reported as 75,000 hens, but has since been revised, Zeagold Nutrition confirmed this afternoon.

The fire on Old Rd, Orini, was reported to Fire and Emergency about 7.45am this morning.

When FENZ crews arrived at the scene, the fire was already "well-involved".

"All 12 staff members on site are safe and unharmed," Zeagold Nutrition chief executive John McKay said in a statement.

He initially said the fire affected four of the 12 barn layer sheds on the property, but later clarified that only two were affected, with the damage less extensive than initially reported.

"We have lost two sheds out of the 12 on site. Engineers and electricians have been on site today to restore power, water and feed to all the remaining sheds.

It’s expected the onsite packing facility will be operational from this evening to ensure all the eggs unaffected by the fire can be packed and delivered to customers.

He said a specialist avian vet is "currently assessing and caring for the birds in the remaining sheds".

"His initial report is that the birds seem to be in good health. They will continue to be closely monitored in the coming days."

McKay said the "cause of the fire is yet to be determined and investigations will continue".

"At this stage the focus is on supporting our team and the wellbeing of the remaining hens at Orini.

"It will take time to rebuild the sheds and restore flock numbers, but I want to assure New Zealanders that we’ll be working hard to continue to supply eggs and get back to full capacity as soon as possible."

He also addressed concerns around New Zealand's egg supply shortage, which is expected to continue for some months.

"The reality is the losses at Orini, represent only 1.4% of the layer hen population nationally so while it’s a tragic loss it won’t have a significant impact on egg supply."

The egg laying farm has been running for nearly two years when the fire occurred, he said.

A FENZ spokesperson confirmed the fire has been contained.

Zeagold is the biggest egg producer in New Zealand, selling its eggs under the Woodland and Farmer Brown brands.