The incident took place late last night when some children were bursting firecrackers outside the shop at Shastri chowk market in Balotara town.
One of the staffers put down the shutter to prevent the crackers in the shop from catching fire, Additional SP Barmer Jassa Ram said.
However, at 1:20 AM a spark entered the shop leading to the fire, he said.
All the seven persons who were present in the shop were trapped inside and killed as the shutter was down, the ASP said.
Those who were killed were identified as 50-year-old shop owner Gaimar Singh, his sons Jalam Singh (27) and Mahendra Singh (23), staffers Kuldeep Singh (28), Kuldeep Singh (22), Swaroop Singh (18), and one Raju Singh (23) who was in the shop to purchase firecrackers, Ram said.
Bodies were handed over to the family members after the post-mortem, the ASP said.