UPDATE, 10pm PT: People are starting to throw the word "meltdown" around. Here is an NHK update reporting that venting has been suspended at the plant because of high radiation levels, and concern over pressure and possible damage to the containment vessel. Here is an AP item with a statement from a Japanese nuclear official with somewhat contradictory info. Al Jazeera: "Japanese nuclear authorities said that there was a high possibility that nuclear fuel rods at a reactor at Tokyo Electric Power's Daiichi plant may be melting or have melted, Jiji news agency reported on Saturday."
Tokyo Electric Power Company (TEPCO) reported a radiation leak at one of its two nuclear power plants in Fukushima damaged by Friday's massive earthquake, according to Japan's Kyodo News agency.
More on the worsening situation around nuclear power plants affected by the quake and tsunami in this New York Times update. The prospects look increasingly frightening.
TEPCO is publishing hourly updates on the situation here, in English.