Japanese authorities have reported that the Tokyo Electric Power Company has detected radioactive materials in seawater at one location near the Southern discharge canal at the Fukushima Daiichi nuclear power plant, the IAEA said.
Samples taken included levels of iodine-131, cesium-134, and cesium-137, the IAEA said.
To study a larger area of the marine environment, the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) plans to measure radioactivity around the plant from 22-23 March.
Seawater will be collected from eight locations, and the Japan Atomic Energy Agency plans to analyse the samples and release results on 24 March.
The analysis will include radionuclide concentrations found in sea water and dose rate in the air.