New Zealand's biggest company, Fonterra, has been hard hit by the disruption to upper North Island gas supplies, with farmers forced to dump tens of thousands of litres of milk.
Gas was cut to 5000 commercial customers from New Plymouth to Northland on Tuesday after a leak was discovered in the Maui gas pipeline.
It forced Fonterra to close 15 of its dairy processing plants in Waikato, Bay of Plenty and Northland.
The Tatua dairy co-operative in Waikato also had to stop processing.
However, on Wednesday evening Fonterra said it expected to have all its milk processing plants in Waikato and Bay of Plenty operating again by Thursday morning.
It did not know when its Northland sites, at Maungaturoto and Kauri, as well as its Tip Top factory would resume operating.
Managing director trade and operations Gary Romano says Fonterra expected to be able to collect and process milk from some farmers in the Waikato and Bay of Plenty from Wednesday night.
He says Fonterra's service centre was contacting those farmers.