(Correction: Tokuda is from Kagoshima, not from Fukushima.)
If what Takeshi Tokuda, Member of the Lower House (House of Representatives) in the Japanese Diet, says is true, the explosion that blew up the Reactor 1 building roof and side walls may not have been an hydrogen explosion as the government has insisted, but something decidedly more serious.
From his April 17 blog entry (original in Japanese):
[Tokuda is writing about his day on April 15, including a visit to Minami-Soma City, which has been designated as "planned evacuation zone". He visited the Minami Soma City General Hospital and spoke with Dr. Oikawa, and the following is what he heard from Dr. Oikawa.]
Then I heard a startling story from Dr. Oikawa.
On the first hydrogen explosion on March 12 [Reactor 1], broken pieces [of...??] and small stones [from the explosion] landed in Futaba-machi, 2 kilometers away from the Plant.そしてその爆発直後、原発の周辺から病院へ逃れてきた人々の放射線量を調べたところ、十数人の人が１０万cpmを超えガイガーカウンターが振り切れていたという。
When the hospital checked the radiation level on the people who escaped from around the nuke plant after the explosion, there were more than 10 people whose radiation level exceeded 100,000 cpm [counts per minute], beyond what could be measured by the geiger counter the hospital had.
[100,000 cpm is the new level that the Japanese government set that requires decontamination. Before the Fukushima accident, the level was 6,000 cpm, and on March 12 it was still 6,000 cpm.]
It is the level that threatens the secondary radiation contamination.
However, it has never been disclosed by the government that it was such a serious situation.
Some people, without stopping by at the hospital and without knowing that they had been exposed to high radiation, may have gone home and hugged their children.
So I re-read the transcript of the press conference given by Chief Cabinet Secretary Edano two hours after the explosion.
He said that there was a hydrogen explosion, but it was confirmed that the Containment Vessel was not damaged.
It was not the explosion within the Containment Vessel, therefore no large amount of radioactive materials would be released, Edano said.
１３日での会見では、バスにより避難した双葉町の住民の皆さんのうち、９名が測定の結果、被ばくの可能性があることを発表した。In his March 13 press conference, he announced that 9 people who had evacuated from Futaba-machi by bus may have been exposed to radiation.
4 of them had the low dose of 1,800 cpm, the highest dose was 40,000 cpm, he said.
Edano also said that according to the experts there would be no serious negative effect on health as long as such matters [radioactive materials] stay on the surface.
Did the government not know about this serious situation at Minami-Soma City General Hospital where more than 10 people were found to have been exposed to high radiation levels?
If the government didn't know, that would cast doubts on the capability of the Prime Minister's Office to gather information, and would be problematic from the point of crisis management; if they knew but decided to suppress the information, that would be the manipulation of information by the government, almost a criminal act.