Japan's fisheries agency said on Saturday fish tested in waters around the wrecked Fukushima nuclear plant did not contain detectable levels of the radioactive isotope tritium, Kyodo news service reported.
Nets were set up on Thursday when plant operator Tokyo Electric Power Company (Tepco) 9501.T began releasing treated radioactive water into the Pacific, angering fishermen and many others in Japan, alarming consumers in neighbouring countries and prompting China to ban Japanese aquatic products.
The agency plans to announce test results daily. Tepco said on Friday seawater near the plant contained less than 10 becquerels of tritium per litre, below its self-imposed limit of 700 becquerels and far below the World Health Organization's limit of 10,000 becquerels for drinking water.
Calls to the fisheries agency for comment were not answered on Saturday.
After a lengthy debate, the government of Prime Minister Fumio Kishida decided on Tuesday to allow the release of 1.3 million tons of treated water from the Fukushima plant, destroyed by a 2011 tsunami because Tepco was running out of storage space.
The utility filters most radioactive elements out of the water but dilutes tritium, an isotope of hydrogen, which is difficult to separate from water.
Cardinals are scheduled to meet on Tuesday to plan Pope Francis' funeral, which leaders from around the world will attend ahead of a conclave next month to elect a new head of the Roman Catholic Church.
Russian President Vladimir Putin proposed on Monday bilateral talks with Ukraine for the first time since the early days of the war, and his Ukrainian counterpart Volodymyr Zelenskyy said Kyiv was eager to discuss a halt to attacks on civilian targets.
Ukraine issued air raid alerts for Kyiv and the country's eastern half as blasts shook the city of Mykolaiv early on Monday, authorities said, hours after the one-day Easter ceasefire declared by Russian President Vladimir Putin came to an end.
US Vice President JD Vance began a four-day visit to India on Monday and will hold talks with Prime Minister Narendra Modi, as New Delhi rushes to avoid steep US tariffs with an early trade deal and boost ties with the Trump administration.