Together with the Mitaka and Shimoyama incidents, it was one of three major criminal cases involving allegations of sabotage blamed by the government on the Japanese Communist Party and the Japan National Railway Union in the immediate post-war era.

[1] Twenty people were arrested and seventeen were convicted in 1953 (four of whom received death sentences), but eventually all were acquitted on appeal,[2][3] and the case was closed without determining the real cause in 1970.

Suspicion immediately fell on Japan National Railway Union, workers at the nearby Toshiba-Matsukawa factory and the Japanese Communist Party, due to recent protests over staff cuts.

During the first ruling of the Fukushima District Court on December 6, 1950, all twenty defendants were found guilty, largely on the strength of confessions forced by the police during interrogation.

Legal proceedings dragged on until 1970, when the defendants were finally awarded compensation from the Japanese government for false arrest and imprisonment.