Fukushima Prefecture deleted the dispersion simulation data it received from the day of the accident
I do not read Japaneses, so not sure what to think of this translation of Tokyo Shinbun (3/21/2012):
The Fukushima prefectural government had the dispersion simulation data of radioactive materials from the Fukushima I Nuclear Power Plant accident from the evening of March 11, 2011 in emails, but lost the data up to the morning of March 15, 2011, our reporter has uncovered by speaking with the people involved. There were explosions at Reactors 1, 3 and 4 during those 5 days, but the prefectural government hasn't shown the simulation data to the municipalities around the plant. The person in charge at the prefectural government says, "The data took up too much space so I deleted it."