NHK has learned that Chinese authorities have suspended the registrations of facilities used by Japanese exporters of seafood.
Japanese firms seeking to export marine products to China are obliged to register their processing, storage and other facilities in Japan with Chinese customs authorities.
In August last year, the authorities suspended imports of Japanese seafood, following a release of treated and diluted water from the damaged Fukushima Daiichi nuclear power plant into the sea.
Sources familiar with the matter say the registrations of exporters’ facilities had been effective until last month.
Other sources close to the Japanese government say the Chinese authorities suspended all the registrations this month.
They say the Chinese side has not provided any explanation to Japan for the latest move.
This comes as the governments have held talks on the release of the treated and diluted water this year.
The government sources say they need to find out why China chose this time to suspend the registrations.
The Fukushima Daiichi nuclear power plant suffered a triple meltdown following the 2011 earthquake and tsunami.
Water used to cool molten fuel at the plant has been mixing with rain and groundwater.
The accumulated water is treated to remove most radioactive substances, but still contains tritium.
Before releasing the treated water into the ocean, the plant’s operator dilutes it to reduce tritium levels to about one-seventh of the World Health Organization’s guidance level for drinking water.