Early indications are that the properties have links with the Van Leeuwen Dairy Group (VLDG) through cattle movements.
"The Hastings and Ashburton properties were identified through our tracing programme and the Winton property was identified through the industry milk testing programme," Gwyn said.
"All of the movements we have been tracing are before July 21, when the disease was first detected and notified to MPI.
"The Hastings and Winton properties are now under a Restricted Place Notice under the Biosecurity Act. This effectively places them in quarantine lockdown - restricting the movement of animals and other risk goods. MPI is working closely with them."
Gwyn said the new developments were not good news.
"We're still analysing what this means for the wider response. We're dealing with a lot of uncertainty. Our investigators are building a picture of stock movements on to and off these farms so we will not be making hasty decisions on next steps.
"While it's really disappointing to have these new properties, it is not totally unexpected. We know that this disease is spread through contact between animals and through the movement of stock – as is the case here."
Agriculture and Biosecurity Minister Damien O'Connor said he was "deeply disappointed'' by the latest detection of the disease.
The disease causes udder infections, abortions, pneumonia and arthritis.
"The fact the disease has been found in the North Island is disappointing to me and, no doubt, will be for farmers too,'' O'Connor said.
"We are still unable to identify the source of the disease and that concerns me."
O'Connor said he would meet with officials to discuss the next steps in dealing with the outbreak.
"I understand this is tough for farmers, people working on these properties and people in these close-knit communities, but everyone is working hard to find solutions.''
Gwyn said the "depopulation programme" was almost complete on the infected Van Leeuwen properties and on track to be completed before Christmas. More than 3500 animals have been culled.
"Our testing and tracing work also continues. MPI has completed more than 55,000 tests and followed up 250 properties.
"We encourage farmers and rural contractors to protect their farms by following standard on-farm hygiene best practice and to ensure their NAIT and all farm records are kept up to date. "
Full information was available at www.mpi.govt.nz
Good on-farm biosecurity and accurate tracing of animal movement is not an option in today's world, it's an imperative, Federated Farmers president Katie Milne said.
Federated Farmers and other industry leaders remain committed to eradicating Mycoplasma bovis, even though today's announcement makes that a bigger but by no means impossible challenge, Milne said.
"Don't rely on others to protect your patch, protect it yourself. In the end, we are all biosecurity officers with a role to play.
Close and repeated contact with an infected animal is still regarded as the most likely way Mycoplasma bovis is spread.
If vets and AI technicians are visiting your property, make sure they have thoroughly cleaned their equipment before they arrive and do so before they leave, and provide hot water and disinfectant for their hands and equipment.
Consider making a footbath and a scrubbing brush handy for the boots of all visitors coming on to, and leaving, your farm.
"Think about your own actions too. If you're visiting a neighbour, clean your boots and any gear you might bring," Milne said.
"We certainly extend our best wishes to them in what will be a stressful time, and we will continue to work closely with MPI and other sector groups on this sensitive and vital issue.
"Federated Farmers has been helping affected farmers where we can and as we are asked. I encourage any of the new farmers to contact us or their local Rural Support Trust if they have any questions or want assistance."
MPI would be holding a public meeting in the Hastings area on the evening of Wednesday December 20. Venue and time will be confirmed on the MPI Facebook page.
