On June 18, 2012, Asahi Shinbun reported that:
The Ministry of Foreign Affairs received the fax from the US showing the contamination map created from the actual data collected by Global Hawk drones via the US Embassy in Tokyo on March 18 and 20 last year. The Ministry of Foreign Affairs told Asahi that it immediately forwarded the fax to the Nuclear and Industrial Safety Agency and the Ministry of Education. NISA and the Ministry of Education both sat on the data.
A Lower House Representative and "Shadow Minister of Foreign Affairs" of LDP (Liberal Democratic Party) describes the event a bit differently.
Itsunori Onodera, a Representative from Miyagi District 6, tweeted on June 18, 2012 as follows:
About the data from the US right after the Fukushima nuclear accident started, the US Embassy asked my office to do something because the Prime Minister's Official Residence wouldn't accept the data from them directly. So I liaised with the PM's Official Residence. However, in the end it was ignored. It is just too irresponsible.
Some of the people responding to his tweet are rather critical of him. They say, "So what did you do then? Did you speak out?"
Mr. Onodera, as with many people at that time - journalists, experts, politicians, bloggers - may have self-censored so as not to cause panic among the population. Or simply, the earthquake and tsunami damage seemed overwhelmingly bigger than the nuclear accident, even after 3 (visible) explosions. (What happened in Reactor 2 is still not known or disclosed.) It was when some people were saying "Let's go out, have fun and spend money so that the economy doesn't contract and deflation further sets in", as I read at that time on an online message board in Japan.
But the government officials at the Prime Minister's Official Residence knew full well what the Fukushima I Nuclear Power Plant accident meant, as Mr. Edano was on record suggesting the evacuation plan for wider areas in Kanto be considered. If what Mr. Onodera says is true, there's some explaining to do for Mr. Edano, Mr. Kaieda, and Mr. Kan.