Faint traces of very low levels of radiation from the stricken Fukushima nuclear complex in Japan have been detected in Sacramento, California, the New York Times reported citing European officials.
The readings, picked up by highly sensitive detectors set up to monitor clandestine nuclear blasts, indicated that the leading edge of a long radioactive plume drifting slowly across the Pacific over the last week has now reached American shores, the daily said Friday.
However, the newspaper cited health experts as saying that with the plume's radiation diluted enormously in its journey across thousands of miles, it would have no health consequences in the US at least for now.
In a similar way, radiation from the Chernobyl disaster spread around the globe and had reached the West Coast of the US in 10 days. Its levels were detectable but minuscule, it said.
Late Friday, the US department of energy confirmed the European statements about the arrival of the radioactive plume in Sacramento, saying the federal station there detected "minuscule quantities" of radiation that posed no health hazard.
The Sacramento readings were made on Air Force equipment shared with the Comprehensive Test Ban Treaty Organisation, an arm of the UN in Vienna. Its mandate is to monitor the global ban on the testing of nuclear arms.
European officials cited by the New York Times said that its global network of detectors - outside Japan - first picked up the presence of the Japanese plume at a station on the Kamchatka Peninsula in Russia.
Then the station in Sacramento Friday began to register the faint radiation, they said. The government declined to release further details.
The daily cited experts, following the plume's movements, as saying it would continue to drift eastward and might arrive in the New York region early next week.
To assure concerned Americans, President Barack Obama had Thursday said he knew citizens were worrying about radiation drifting across the Pacific.
"So I want to be very clear," he said at the White House. "We do not expect harmful levels of radiation to reach the US, whether it's the West Coast, Hawaii, Alaska or US territories."