The incident occurred at Dhana Lakshmi crackers factory in morning hours.
A police official said all the three workers suffered burn injuries and condition of one of them is critical.
The trio are identified as Rotta Apparao (40) L. Kameswari (50) and Kurada Satyavati (54).
The Karapa Police have registered a case.
The official said the factory had a valid license and the cause of the explosion is investigated.
No arrest has been made so far.
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