The fire was discovered in a train on the U-Bahn's 3 line, which quickly filled with smoke, authorities said on Thursday. Passengers were able to safely exit the train at the next station, meanwhile a metro on its way to the station was stopped and sent back to the previous stop.
Fire fighting efforts were difficult due to the heavy smoke and the blaze was extinguished about one hour after rescue workers arrived. The underground station was then cleared of smoke and train traffic resumed a few hours later.
Six passengers and the conductor were treated on the scene for smoke inhalation. Three people were transported to a local hospital for observation.