Following up this article..Reactor4 had one explosion and 2 fires in March 2011
Tepco states the second fire at reactor4 started at 5:45 of 3/16/2011, and the fire was naturally “missing” at 6:15 (so does Ministry of Economy, Trade and Industry), but on the same day, Yomiuri newspaper reported the fire was not distinguished even at 10:00, smoke was coming up from the building.
Tepco reported to NISA that they saw fire through the hole on the wall, which is made by the explosion on 3/15 [LINK]. They found fire at the North-West corner of reactor4 building at 5:45 3/16/2011. Because the radiation level is too high, they can not get close, it is not known what is burning. Tepco reported it to the government and Fukushima prefecture. Tepco staff saw the fire missing at 6:15, but white smoke is still coming up from the building, the fire is not extinguished at the moment of 10:00. 4 fire-engines and 13 fire fighters tried to approach but can not go close. The fire was observed near SFP4. It is assumed that the water level decreased because of the heat by the spent fuel, fuel rods got above the surface to cause fire.
To inject water, Tepco was planning to corporate with Japanese self defense force and US army to use helicopter on 3/16. At 6:00, the wind blows from North West, wind speed is 2m/s.
The fire was not extinguished at least by 10:00 of 3/16/2011. It is not reported how much damage it caused to the reactor4 building.