The United States is deploying extra radiation monitors to western US outposts Alaska, Hawaii and Guam to detect any fallout from Japan's crippled nuclear plant, an official said Thursday.
The US Environmental Protection Agency (EPA) is sending the portable units, to boost an existing network of monitors, to Dutch Harbor in the Aleutian Islands as well as Juneau and Nome in Alaska, said the official.
Alaska already has detectors in Anchorage and Fairbanks. The decisions to deploy the units came "this week" and the official could not say when they would begin operating.
The official, speaking on condition of anonymity, stressed that the move is precautionary. "We don't expect any significant amounts of radiation," he said, adding that the EPA was expected to brief reporters later in the day.
The US western states of California, Oregon, and Washington State have also been monitoring for any increase in radiation levels from Japan's Fukushima nuclear power plant, damaged by last Friday's earthquake and tsunami.
Some experts says radioactivity could reach the US West Coast as early as Friday, although well below levels which could harm human health.
The main US manufacturer of potassium iodide pills, which can protect against the effects of radiation, ran out of supplies within hours of the Japanese earthquake, according to the company's boss.
Explore further: China's struggle for water security