An animal advocacy group says it had previously investigated the Waikato farm where 400 pigs burnt to death over the weekend.
Farmwatch spokesman John Darroch said the fire was both tragic and predictable.
He visited the shed that burnt down last last year, describing it as derelict, with heat lamps being used inside what appeared to be home made plywood boxes.
There were no sprinklers or means of escape for the pigs.
Mr Darroch said the industry was clearly putting profits ahead of animal welfare.
