That, according to Jiji Tsushin, is captured in the video TEPCO released and has been allowing the media to view at TEPCO's Headquarters in Tokyo. The company has made 1.5-hour video for the public consumption, but the media has been reporting new findings in the video only they are allowed to view, and this is one of the latest.
TEPCO was ready to hold a press conference immediately after it learned of the rising pressure in Reactor 3 in the early morning on March 14, 2011. But an elite bureaucrat at the Nuclear and Industrial Safety Agency at an elite ministry (Ministry of Economy, Trade and Industry) needed to find his boss to decide whether TEPCO could hold a press conference to tell the general public of such a terrible news. This bureaucrat told TEPCO, "Absolutely not", because he couldn't find his supervisor and he didn't want to be the one in charge at NISA when this bad news was disclosed.
Fit for an agency whose Director General, being a liberal arts major as he claimed as an excuse, went home from the Disaster Response Headquarters at Prime Minister's Official Residence in the evening of March 11, 2011 and never returned.
I suppose this official knew, as a matter of fact, what had happened to the NISA official who had talked about a possible core melt in Reactor 1 at the noon press conference on March 12, 2011. He was dismissed immediately after, by the Kan administration.
From Jiji Tsushin (8/13/2012; emphasis is mine):
Delay in disclosure because of NISA's order - rising pressure in Reactor 3 right before the hydrogen explosion because [NISA official] "couldn't locate my supervisor".
On the morning of March 14 last year right before the hydrogen explosion at Reactor 3 at Fukushima I Nuclear Power Plant, TEPCO was about to give a press conference on the news that the parameters that monitored the pressure inside the Reactor 3 Containment Vessel indicated a sudden spike in pressure but the company was ordered to wait by the Nuclear and Industrial Safety Agency, [we learned] on August 13 [after viewing] TEPCO's teleconference video.
According to the video, [TEPCO] learned of the abnormal rise in pressure inside the Containment Vessel of Reactor 3 at about 6AM on March 14, 2011. Plant Manager Masao Yoshida feared for a hydrogen explosion and instructed the workers at the scene [near Reactor 3?] to take shelter. However, it was not until after 9AM that day when NISA finally made the announcement of this information, about 2 hours before the hydrogen explosion at the Reactor 2 building.
TEPCO's press relation team at Fukushima I Nuke Plant had prepared the press release, but the person in charge at the plant said during the exchange with TEPCO Headquarters, "The national government has ordered us not to, and we are waiting, without giving any press conference." A person at TEPCO Headquarters was heard saying, "About this event, NISA has stopped all communication to the press, and we as the plant operator are told not to disclose anything."
Further, at TEPCO's Headquarters, someone was recorded saying "[Additional] information about the press release. I've confirmed it with NISA, and their opinion is "absolutely not", this press release must not be made, it's a strong demand and order."
On this delay in disclosure, NISA [official] explains, "[I] couldn't get hold of my supervisor, so I asked TEPCO to delay the release of information."
In the final report by the National Diet Fukushima Accident Independent Investigation Commission released in July, the Commission pointed out "(Until the announcement by NISA) citizens were not informed of this critical situation for (at least) more than 2 hours."
Reactor 3 building would still have blown up regardless of whether TEPCO or NISA held a press conference, but it might have made a tremendous difference in alerting the residents in the surrounding areas and evacuate them sooner. After all, from last year's articles and my own posts, Reactor 3's explosion was so downplayed by the government that residents were given conflicting information about whether there was an explosion at all, several hours after the explosion took place.
There were many people still remaining in Namie-machi, Minami Soma City, and people even in Futaba-machi and Okuma-machi (whose residents should have been evacuated by then), looking for survivors of the earthquake and tsunami on March 11, 2011.
We would never know, but I always wonder. What would have happened if TEPCO had said "NO" to NISA's order and held a press conference? What could NISA do? Fire TEPCO? Fine the company for not following orders? Sue the company for fanning "baseless rumors" and create panic?