California is closely monitoring efforts to contain leaks from a quake-damaged Japanese nuclear plant, a spokesman said Saturday, as experts said radiation could be blown out across the Pacific.

While officials downplayed any immediate danger, the US Nuclear Regulatory Commission deployed two experts to Japan, where the Fukushima plant, which was rocked by a large explosion earlier in the day in the aftermath of Japan's strongest-ever earthquake.

"At present there is no danger to California. However we are monitoring the situation closely in conjunction with our federal partners," Michael Sicilia, spokesman for California Department of Public Health, told AFP.

"California does have radioactivity monitoring systems in place for air, water and the food supply and can enhance that monitoring if a danger exists," he added.

He was speaking as Japanese authorities moved to calm fears of a meltdown and said a huge explosion Saturday had not ruptured the container surrounding the reactor, although there had already been some radiation leakage prior to the explosion.

Experts have suggested that, if there were a reactor meltdown or major leak at Fukushima, the radioactive cloud would likely be blown out east across the Pacific, towards the US West Coast.

"The wind direction for the time being seems to point the (nuclear) pollution towards the Pacific," said Andre-Claude Lacoste of the French Nuclear Safety Authority, briefing journalists in Paris on the Japanese crisis.

The Nuclear Regulatory Commission meanwhile said it has sent two experts to Japan, and has been in regular contact with Japanese officials about the crisis.

"We have some of the most expert people in this field in the world working for the NRC and we stand ready to assist in any way possible," commission chairman Gregory Jaczko said in a statement announcing the deployment.

He said the pair were experts in boiling water nuclear reactors and are part of a broader US aid team sent to the disaster zone.

Earlier the NRC said it was "examining all available information as part of the effort to analyze the event and understand its implications both for Japan and the United States."

While US nuclear experts acknowledged the seriousness of Japan's reactor crisis, some stressed that taking steps in the United States such as distributing iodine tablets -- which prevent iodine 131 from being absorbed into the body -- would be "vastly premature."

"It's a big ocean. These (radiation) releases are essentially going to be at ground level," said Ken Bergeron, a physicist who has worked on nuclear reactor accident simulation.

"We should not confuse it with health issues in the United States."

Japan is roughly 5,000 miles (8,000 kilometers) from the US West Coast.

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(c) 2011 AFP