The incident took place when the labourers were filling bags with gum in the factory, they said.
Some labourers who were standing near the wall, however, escaped unhurt. A part of the roof also collapsed.
The deceased were identified as Manoj, Chandan Shah, Ranveer, Janardhan, Kashi Mukhia and Jugeshwar, all residents of village Dubehi in Khagaria district of Bihar, police said.
Later, the bodies of the deceased were taken out with the help of the villagers and sent to civil hospital in Hisar for conducting post-mortem examination.