The Matsumoto incident was an outbreak of sarin poisoning that occurred in Matsumoto, Japan, in the Nagano prefecture, on the evening of June 27 and the morning of June 28, 1994.
Seven people were killed and over 200 were harmed by sarin gas that was released from several sites in the Kaichi Heights neighborhood. The first calls to emergency officials occurred around 11:00 p.m.; by 4:15 a.m. the following morning, six people had died from the poison. On July 3, officials announced that the toxic agent had been identified as sarin by gas chromatography.
The Matsumoto incident preceded the better-known attack on the Tokyo subway in 1995. Several Aum Shinrikyo members were found guilty of masterminding both incidents. These two instances are the only known use of chemical agents by a terrorist group. Combined, the attacks resulted in 19 deaths and thousands of people requiring hospitalization or outpatient treatment.