The blast occurred in the ammonia condenser of the unit at the Jawaharlal Nehru Pharma city, situated on the outskirts here when 35 workers were working, Deputy Commissioner of Police (Zone-II) G Ramgopal Naik said.
Around 15 workers fell ill after in-hailing ammonia gas, of which condition of two is reported to be serious, Naik said, adding the injured are being treated at different hospitals.
The deceased was identified as K Ramakrishna from Vizianagaram. He was working as an operator at the chilling unit, police said.