A large fire "totalled" a stockfood factory south of Ashburton and sent three firefighters to hospital.
Crews were first called to the blaze at SealesWinslow, which makes feed for livestock, at 7.40pm yesterday.
Three firefighters suffered minor burns from embers and two remain in hospital.
Fire and Emergency area commander Stephen Greenyer said they had immediate first aid and were taken to hospital as a precaution and for extra treatment.
Mr Greenyer said the 100m by 50m shed had pallets and machinery inside.
"It's a big fire. Obviously the shed is totalled now."
Most of the nine appliances and eight tankers left the scene about 2am. Two fire trucks, from Timaru and Christchurch, stayed at the scene to monitor the fire.
More crews and heavy machinery will be brought in this morning to ensure the fire is fully out, and fire investigators will work to determine the cause.