It was during the rush hour and the train was quite full - literally packed.
Approx. 1,300 people had to walk to the nearest station (about 200m away) and it took about 2 hours before all the passengers safely evacuated, according to the news.
About 10 people felt sick and taken to hospital, but fortunately none was seriously ill.
The weather was getting cool but in a packed train it must be stifling and could be rather hot, I feel sorry for those who trapped in the train.
The cause of the electricity mulfunction seems to be that someone failed to turn on one of the main switch at the control centre or something, according to Yomiuri Online.