A group of former fishermen Monday filed an unprecedented lawsuit seeking compensation from the government for failing to disclose, for decades, records of their exposure to radiation from U.S. hydrogen bomb tests in the Pacific Ocean in 1954.

A total of 45 people, mostly from Kochi Prefecture and including families of deceased fishermen, are seeking ¥2 million each, according to the lawsuit filed at the Kochi District Court.

It is the first time a compensation lawsuit has been filed against the state in connection with the hydrogen bomb tests conducted on Bikini Atoll in the Marshall Islands. The tests began with an explosion code-named Castle Bravo on March 1, 1954, a lawyer for the plaintiffs said.