The accident happened on Sunday night in the Dowli area of the region.
The top local administration official, Khushal Khan, told AFP the bodies of the seven had been recovered and taken to their home town of Shangla.
Two other local officials confirmed the incident.
Most coal mines in Pakistan are notorious for poor safety standards and facilities. Similar deadly accidents have occurred in the past.
Earlier on November 27, an explosion inside a coal mine in Tora Wari of Hangu district killed two miners and injured two others.
According to the owner of the mine, six labourers were working when the incident occurred. Two of them, however, had just stepped outside and were safe.
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