At least 12 labourers were killed when a coalmine collapsed in south-western Pakistan after a gas explosion on Wednesday, officials said, in the latest accident in one of the most unsafe countries for mining. The explosion occurred overnight in the town of Harnai in the province of Balochistan when at least two dozen workers were inside the several-metre-deep mine, local official Qismatullah Tareen told dpa. Rescuers scrambled for several hours through the rubble to retrieve bodies and pulled at least 12 injured people out alive, said Mohamed Ahmer from the provincial rescue department. Gas ex…