The US has downgraded advice that had sent diplomats' families fleeing Japan in the wake of a nuclear emergency, allowing them to return to the country, a statement said Friday.
"The Department of State has lifted voluntary authorised departure, allowing dependents of the US government employees to return to Japan," said a statement issued in Washington.
The statement said the risk from the crippled Fukushima Daiichi nuclear plant, where workers are battling to cool overheating reactors, had lessened.
It said its advice was "based on the much reduced rate of heat generation in the reactor fuel after one month of cooling and the corresponding decay of short-lived radioactive isotopes"
Washington continues to recommend its citizens stay outside a 50-mile (80 kilometre) radius of the plant, far larger than the 20-kilometre exclusion zone mandated by the Japanese government.
The authorisation to return to Japan applies to around 600 family members of diplomats in the US embassy in Tokyo, the consulate in Nagoya and a language school in Yokohama.