Hansells also has premises on Rockfield Rd which back on to the Botha Rd property.
At Rockfield Rd, Hansells makes steamed puddings and its oil-based spread.
McKay said office staff moved from Rockfield Rd and elsewhere into the new building a year ago.
"It's been a gradual progression into the site. It's only now that we have the new bakery up and running so we've now completed this part of our expansion plan.
"We have over 380 employees and there's been 30 jobs created with the opening of the new factory because new baking lines have been built which enables expansion into further brands," McKay said.
"This enables a whole lot more innovation so with the new ovens we're putting in, it allows us to enhance products. Cakes, loaves and tarts will be first new products."
About 60 per cent of Hansells' products from the Auckland sites are now exported.
Hansells is a privately owned company, started 77 years ago, with the majority of shares in New Zealand hands.