An improperly balanced wheel-load was the probable key cause of the subway train derailment that killed five passengers and injured 60 others on Tokyo's Hibiya Line in March, a Transport Ministry expert panel said in its interim report released Tuesday.
Later the same day, Kiyoshi Terashima, head of Hibiya Line operator Teito Rapid Transit Authority, said he had tendered his resignation to Transport Minister Toshihiro Nikai to take responsibility for the accident.
"Since the accident, I have thought of eventually taking responsibility," Terashima said at a news conference held at the ministry.