Carter Holt Harvey sawmills at Putaruru in south Waikato and Mount Maunganui are set to close, resulting in the loss of 316 jobs.
Workers at the plants were told of the planned job cuts on Tuesday afternoon, however Carter Holt Harvey is refusing to make any comment.
The Engineering, Printing and Manufacturing Union has confirmed Carter Holt's intention to close the plants in November after a consultation period with workers.
More than 200 jobs will go at the Putaruru plant, which manufactures timber framing, and just over 100 jobs at the plywood mill at Mount Maunganui.
EPMU national secretary Andrew Little says the union wants to put forward ideas to try to save the plants - but cannot until more information and figures are recieved from Carter Holt Harvey.
Mr Little says the company has told workers a drop in domestic demand has resulted in over-capacity.
He says the low New Zealand dollar will make exports more viable and may provide some hope of keeping the mills open.