Is there really a nuclear meltdown in Japan?

Now another nuclear power plant is having an emergency and this time it could be a meltdown. The Japanese officials keep saying that it's not that bad but other people are saying that a meltdown is happening right now. If there was very bad nuclear meltdown, some radioactivity could possibly drift through the air to America, but the radiation that would get here would not be serious. Japan would be devastated though. At this point, there COULD be a nuclear meltdown happening.