The incident occurred due to a buildup of toxic gas in the mine when about 13 workers were working inside, Orakazi division police officer Nazeer Khan said.
He said three people were still stranded inside the mine and rescue work was underway to get them back.
The injured workers were taken to a nearby hospital and are in critical condition, local media reported.
Pakistan has more than 184 billion tons of coal and produces 4 million tons of coal a year. However, mines often see frequent accidents due to their unsafe working conditions and primitive mining methods.
According to the Pakistan Central Mine Labor Federation, between 100 and 200 workers are killed or injured in coal mine accidents across the country every year. ■