The incident took place in Badapada village in Pattamundai Rural Police Station area in the evening.
One person, identified as Ratnakar Mallick, had illegally stored petrol in a drum for the marriage procession of his son. However, the drum, which was kept inside a thatched roof house, accidentally caught fire due to a short-circuit and the explosion took place, a police officer said.
The three-year-old boy was burnt to death and five others were injured. Of them, the condition of the 14-year-old boy is stated to be serious and he has been shifted to SCB Medical College and Hospital in Cuttack, Pattamundai Rural Police Station inspector-in-charge Padmalaya Pradhan said, adding four others were undergoing treatment at the sub-divisional hospital.
Fire tenders were pressed into service and the blaze was brought under control, he said.
The deceased has been identified as Gulu Mallick, he said, adding no one has been arrested so far.