Eighty-three people in the western German city of Essen had to leave their homes during the night because the safety of their building could not be guaranteed, a spokesman for the Essen fire brigade said on Saturday morning. A cavity had been discovered underneath the building, Nico Blum explained. The fire brigade’s operation began at around 10 pm (2000 GMT) on Friday and ended at around 3 am on Saturday. Access to a more than 100-year-old ventilation tunnel from the region’s mining history is located under the multi-storey building in the city’s Freisenbruch district, a city spokeswoman expl…