At least 13 people have been killed and more than 20 others injured by an explosion in a mineshaft in Russia. Officials say 67 out of 103 miners inside the pit escaped unharmed. The blast ripped through the Listvyazhnaya site as a 45-strong team was repairing part of the mine, which lies near Russia’s border with Mongolia.Authorities say that it is too early to determine what caused the incident, although it is known that the explosion was triggered by methane. Accidents are common in Russia’s loss-making collieries. In many, safety procedures have remained the same since Soviet times. But the owner of the Listvyazhnaya mine says there are no reasons to believe that poor maintenance of the shaft or faulty equipment was to blame.