On the video of the head office 30 minutes after reactor3 exploded at 11:01 of 3/14/2012, one of the executive managers, Takahashi stated,
” We don’t know if it was really a hydrogen explosion, but because the government, Nuclear and Industrial Safety Agency said it was a hydrogen explosion, let’s announce it was a hydrogen explosion. They’re trying to say it was the same explosion but different reactor number, aren’t they.”
Takahashi was making the statement for press conference with Shimizu, former Tepco president.
http://fukushima-diary.com/2012/08/tepco-we-dont-know-but-lets-say-reactor3-had-a-hydrogen-explosion-because-nisa-said-so/