In the article bws48 linked to above, the spokesperson said: "At this point, there has been no major change to the level of radiation leakage outside (from before and after the explosion), so we'd like everyone to respond calmly...". They did report the level before the explosion (I'm not a physicist, so the number meant nothing to me--something like 1,000 mSv IIRC) and they're saying it hasn't changed, so we essentially know what it is after the explosion. They also reported that the containment vessel was not breached.

Besides the points Teshlinker raised which apply to all large chaotic events, let's also keep in mind the time difference and the additional time lag of the news cycle. While we're Monday morning quarterbacking during the day here in the US, it's the middle of the night in Japan. It's noon here in California and they still won't wake up for several more hours in Japan. By the time people do more work in the morning, arrange press conferences in Japan and finally report it here, it's already quite late. Maybe too late for many of us before we go to bed, so we won't hear new information until the following day.