On the evening of July 27, 2025, a chlorine-based gas leak occurred at Mitsui Chemicals' Omuta Plant in Fukuoka Prefecture, Japan. According to the company’s second official statement released on July 28, the incident began around 5:31 p.m. when gas detectors near the plant's degassing tower were triggered. Emergency shutdown procedures were immediately initiated, and water spraying was employed to contain the leak.

As of 3:00 p.m. on July 28, a total of 82 individuals—including police and fire personnel—had received medical attention, with 11 people remaining hospitalized for observation. While damage assessments are ongoing, the TDI production unit remains completely shut down, and the timeline for resumption has yet to be determined.

Mitsui Chemicals has established an emergency response task force and is cooperating with relevant authorities to investigate the cause of the incident. The company has pledged to implement appropriate measures to prevent future occurrences. The impact on product supply, including inventory levels, is currently under evaluation.