The cracker factory, located near Khob Darwaza area in the city caught fire around 4.45 PM, in which eight women, four men and three children were killed, Additional Superintendent of Police (ASP) Pankaj Shrivastava told PTI.
According to police, the factory belonged to one Yusuf Hussain, who was immediately detained.
The cause of the fire was yet to be known.
Fire-tenders were rushed to the site, which managed to control the blaze after over an hour.
Around four persons also suffered serious burn injuries and were rushed to a hospital, police added.
Police ask websites to remove private pics of Rai, Digvijaya
EC to consider army chief appointment issue
Must-try recipes from India!
23 killed in militant attacks in Assam, curfew imposed
Pak summons Indian diplomat over visa denial to 500 pilgrims