SAN FRANCISCO – Federal and state officials sought Friday to dispel fears of a wider danger from radioactivity spewing from Japan’s crippled nuclear reactors, saying testing indicated there were no health threats along the West Coast of the U.S.

Driven by winds over the Pacific Ocean, a radioactive plume released from the Fukushima Dai-ichi complex reached Southern California on Friday, heightening concerns that Japan’s nuclear disaster was assuming international proportions.

However, the results of testing reflected expectations by International Atomic Energy Agency officials that radiation had dissipated so much by the time it reached the U.S. coastline that it posed no health risk whatsoever to residents.

The U.S. Department of Energy said minuscule amounts of the radioactive isotopes iodine-131, iodine-132, tellurium-132 and cesium-137 had reached a Sacramento monitoring station tied to the U.N.’s Comprehensive Test Ban Treaty Organization, but the readings were far below levels that could pose any health risks.

A detector at the Pacific Northwest National Laboratory in Washington state earlier this week also detected trace amounts of xenon-133 — a gas produced during nuclear fission — the DOE said.

The doses that a person normally receives from rocks, bricks, the sun and other natural background sources are 100,000 times the dose rates detected at either location, the DOE and the U.S. Environmental Protection Agency said in a joint statement.

The statement confirmed statements from diplomats and officials in Vienna earlier in the day.