While six members of the family asphyxiated to death, one died due to injuries caused by the blast, Dahod District Collector Mamta Varma told PTI.
"The families had stored potash in order to make cheap firecrackers at home", Varma added.
Preliminary investigations have indicated that the blast occurred due to a spark while the cracker preparation was underway, police added.
A detailed inquiry would be conducted by the police and raids were being carried out to check such illegal activities, police added.