The workers suffered 100 per cent burns, when the boiler in which tyres were being burnt for extracting oil, exploded.
The six were admitted to the Government hospital here.
While one worker died early yesterday, the other four died last night, hospital officials said, adding, another worker succumbed to injuries this evening.
Police said four persons-- the managing director of the unit, Balaguru, his two sons and the supervisor-- were arrested in connection with the incident, last night. They were produced before a local court which granted them bail.
CITU district treasurer S Krishnamurthy submitted a memorandum to the Collector Archana Patnaik seeking a judicial probe into the incident.