NHK has learned that the security guard who rushed to the scene of the fire at Shuri Castle in Okinawa Prefecture last week did not carry a fire extinguisher. He had thought that an intruder set off the heat sensor installed on the first floor of the castle's main hall.
The fire broke out shortly after 2:30 a.m. on Thursday.
Sources told NHK that the guard says when he got to the hall he saw smoke at the northeastern side of the building but did not have a fire extinguisher with him.
Heat sensors had been installed on each of the three stories of the main building. But there were no smoke detectors on the first floor.
A senior official of the Japan Association of Fire Protection Engineers, Hiroaki Suzuki, said early stages of a fire emit a lot of smoke when the temperature is still low.
He said the fire at the castle may have been detected and put out sooner if a smoke detector had been installed on each floor, noting that early-stage firefighting was not effective.