The U.S. Navy asked the Japanese government to hand over detailed data about the release of radiation-contaminated water into the sea from the Fukushima No. 1 nuclear power plant, government sources said Friday.

After Tokyo Electric Power Co. began discharging the water with a relatively low level of radiation, the U.S. Navy asked the Defense Ministry and the Self-Defense Forces to provide the data, such as the schedule of water discharge, its extent and spread within the sea, as well as the density of radioactive substances.

The U.S. Navy said it made the request over concern that its vessels, which have equipment to desalinate seawater for drinking and other daily needs, could take in radioactive water and damage the health of its sailors.