The incident took place around 7.30 am when the victims spotted a bag on the road near Babul Chowk in the town.
Curious, they opened it and found 'missile' bottles (used by fishermen in the district). When they unsealed the bottles, an explosion occured injuring the four, they said.
The bottles filled with glass splinters using air pressure are thrown into ponds to catch fish. When it bursts, it kills the fish following which they are netted.
Immediately after the incident near the busy Dattani Mall, onlookers rushed to the spot, creating panic in the area. However, the situation was brought under control, when police ruled out the use of any explosives.
The injured have been admitted to local civic hospital, police said.