The Matsukawa derailment(松川事件,Matsukawa jiken?) happened on August 17, 1949 when a passenger train hauled by a JNR Class C51steam locomotive (C51 133) derailed and overturned between Kanayagawa and Matsukawa stations on the Tōhoku Main Line in Japan, killing three crew members. It was reported that the tracks had been sabotaged, which the government blamed on the Japanese Communist Party and the Japan National Railway Union. Twenty people were arrested and charged with organizing a conspiracy, and seventeen were convicted in 1953, but all were eventually acquitted on appeal, and the case was closed without determining the real cause in 1970. Afterwards, journalists reported several instances of confessions from a "real perpetrator", which were all unsatisfactory.
In 2010, a special research facility opened dedicated to investigating the incident. Newspapers reported the prosecution as a "miscarriage of justice", but actually it was contemporary with the murky Mitaka and Shimoyama incidents where foul play is highly likely.