A concrete tomb containing more than three million cubic feet of nuclear waste is reportedly cracking under the strains of climate change.
Officially known as the Runit Dome, the structure holds the radioactive waste produced by the 67 nuclear bombs which were detonated on the Marshall Islands between 1946 and 1958.
According to an investigation by the Los Angeles Times , the US government also conducted a dozen biological weapons tests on the islands before mixing the lethal debris and soil with concrete and burying it in the dome.
Despite being buried, the newspaper investigation found evidence that the dome - which locals refer to as "The Tomb" - is leaking.
The rising level of the ocean water means that the waters around the dome rise every year, and Los Angeles Times reporters found evidence of coral bleaching and fish kills nearby, as well as health impacts on local residents.
Although officials in the Marshallese government have requested assistance from the US, the American authorities have said the dome is on their land and is therefore their responsibility.
Hilda Heine, the president of the Republic of the Marshall Islands, has questioned how the nuclear waste could belong to the islands if the Marshallese did not produce it.
A scientific study published earlier this year suggested that levels of radiation in some parts of the Marshall Islands are similar to those near to Chernobyl and Fukushima.
The Marshallese government made a compact with the US in 1986 and an international tribunal set up two years later found that the US should pay $2.3bn (£1.7bn) to address property and health claims.
However, US Congress and courts have refused to do so. The LA Times reports that $4m (£3.1m) has been paid to date.
Its investigation also claims to have discovered 130 tons of soil being taken from a nuclear testing site in Nevada in the US and buried within the dome, material which was never previously disclosed to the Marshallese.
This, the newspaper reports, "could give Marshallese leaders fresh ammunition to challenge the 1986 compact, which is up for renegotiation in 2023".
There are also suggestions that the Chinese government may decide to pay attention to the troubles of the Marshallese as it attempts to gain favour and influence throughout the Pacific.
Of the 4,000 US servicemen who spent three years tackling the debris, six died during the process, the newspaper said, adding hundreds of others developed illnesses including cancers which were connected to radiation exposure.
Sea levels are rising almost three times as fast around the Marshall Islands than the global average, according to scientists.
Experts say the waters around the Marshall Islands could be five feet higher by the end of the century - causing the nuclear tomb to crack and spill its lethal waste into the ocean, with devastating effects.