A woman suffered burns when she tripped and fell into hot water at Ashburton's Talleys plant.
The woman, believed to be in her 30s, was flown to Christchurch Hospital after the accident last night, plant manager Grant Nicholson said.
Although the burns were serious, she was expected to make a full recovery.
Mr Nicholson said taps had been opened up to send hot water down a drain - something they'd always done - but last night the woman slipped and fell in to the water.
He said the water was about 80degC when it left the vessels, so would not have been boiling.
"But because she fell forward it sort of got her from head to toe," Mr Nicholson said.
Mr Nicholson said it was possible the incident could have been avoided and it would make the company rethink its processes.
A Department of Labour spokesperson said the matter was being investigated.
The Talleys Ashburton plant processes vegetables.