The Matsukawa derailment (松川事件 Matsukawa jiken) happened on August 17, 1949 when a passenger train hauled by a JNR Class C51 steam 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 convicted but all were eventually acquitted. The perpetrators of the alleged sabotage were never found.