The blast occurred in a coalmine in Doli area of Orakzai agency due to accumulation of poisonous gas when labourers were busy in routine work, an official said.
Local people and labourers retrieved the bodies from the mine. All the deceased hailed from Shangla district of Khyber- Pakhtunkhwa.
The bodies were sent to their native areas after completion of legal formalities.
There are more than 4,000 coalmines in Orakzai tribal agency and over 3,000 labourers work in these mines. Most of the coalmines in Orakzai are notorious for poor safety standards and facilities.