The mishap occurred due to a methane gas blast inside the coal mine.

As per Dawn News, the incident occurred in coal-rich Chamalang area of Dukki district.

Dukki's district police officer, Sardar Hashim Khan, told the news paper one coal miner sustained serious injuries as a result of the blast. 

Khan told the Pakistani newspaper all the victims, two of whom were siblings, belonged to the same family from neighboring Afghanistan.  

"Miners were extracting coal from thousands feet inside the mine when the tragedy struck," a levies official told Dawn News.