A Cold War-era concrete “coffin” brimming with atomic waste is leaking radioactive material into the Pacific Ocean, United Nations Secretary General Antonio Guterres warned. The dome was built to contain the nuclear waste that was created when the U.S. and France conducted atomic tests in the Pacific between 1946 and 1958. “The Pacific was victimized in the past as we all know,” said Guterres, according to AFP. The structure is on the Enewetak Atoll in the Marshall Islands; Guterres described the dome as “a kind of coffin” designed to contain nuclear material. Thousands of indigenous island people were evacuated or exposed to radioactive fallout when the U.S. carried out dozens of nuclear weapons tests in the area. The bombs tested included the 1954 Bravo hydrogen bomb, which was 1,000 times stronger than the atomic bomb dropped on Hiroshima.