Only after World War II did the secret spill: Ōkunoshima, located in the Inland Sea of Japan between Hiroshima and Shikoku, was the top-secret site for manufacturing chemical warfare. When the factories were closed down, a number of exotic wild rabbits were seen freely roaming the island. They were assumed to have been the test subjects for the chemical weapons, which the military failed to eradicate when the factory was demolished.

In this photo released by Xhinhua News Agency, a rescuer evacuates residents near the site of a chemical plant blast in Zhangzhou, southeast China's Fujian Province Tuesday, April 7, 2015. Six people have been hospitalized and hundreds of firefighters deployed to battle a blaze sparked by an explosion at Goure PX Plant that produces the toxic chemical paraxylene, officials said Tuesday. (Photo by Wei Peiquan/AP Photo/Xinhua)

A woman walks past as South Korean soldiers participate in an anti-chemical and anti-terror exercise as part of the 2023 Ulchi Freedom Shield (UFS) at subway station on August 22, 2023 in Seoul, South Korea. The 11-day exercise, which features drills including the handling of chemical and biological attacks, is a regular joint exercise between U.S. and South Korean troops. (Photo by Chung Sung-Jun/Getty Images)

A general view of the landslide-hit Miancu Village on July 3, 2011 in Maixian County, Sichuan Province of China. Eight people are still missing after a dormitory building of a chemical plant was hit by a rain-triggered mudslide in Maoxian County on Sunday morning. Rescue efforts are underway. (Photo by ChinaFotoPress/Getty Images)

A copper plated Oscar statuette is run through a series of chemical baths at Epner Technology in the Brooklyn borough of New York, Tuesday, January 17, 2017. Every Oscar fist-pumped or tearfully cradled by Academy Award winners is first cast, buffed and fussed over by people far from Hollywood who have spent the last several months making 60 identical gold Oscars for the Feb. 26th awards. (Photo by Seth Wenig/AP Photo)

A man drives a car loaded with electronic and household appliances the Dbayeh highway, at the northern entrance of Lebanon's capital Beirut, on August 11, 2020, following a huge chemical explosion that devastated large parts of the city. (Photo by Joseph Eid/AFP Photo)