The accident occurred at Kamal Steel Mills around 4am on Sunday, said Kadamtoli Police Inspector (Investigation) Md Kamruzzaman.
The injured workers were identified only as Russel, 32, Redwan, 25, Sifat, 28, Shohag, 26, Babar, 35, Dulal, 35, and Sujon, 28.
They were taken to Dhaka Medical College Hospital’s Sheikh Hasina National Burn and Plastic Surgery Institute.
Among the victims, Babar had 6 percent of his body burnt, Dulal 10 percent and Sujon suffered 19 percent burns, said Abdul Khan, a sub-inspector at the hospital’s police outpost, citing doctors.
The others suffered minor burns on their bodies and were released after receiving first aid.
According to the factory’s supervisor Sanjit Mandal, the seven were melting iron at night when the flames from the furnace suddenly erupted and caused them burn injuries.