The labourers had put the raw material in the furnace for melting. The furnace then developed a leak and the labourers came in contact with the substance, Additional SP (Rural) Ramprakash Sharma told PTI.
They were rushed to the SMS Hospital where five of them died while undergoing treatment.
Two are critically injured and are still under the supervision of doctors.
The deceased were identified as Raju Luhar (23), Hiralal Luhar (30), Singhasan Jatav (28) Sukhdev Jatav (18) and Siabai Gaur (35) while the injured were Rajendra Singh (41) and Anandi Tkav (18).
"Family members have been informed about the accident and a post mortem will be done on their arrival," Sharma said.
However, no case has been registered as investigation in the matter is still on, he added.