The fire is believed to have started on the first floor of the main hall in the early hours of October 31. Firefighters took 11 hours to extinguish it, by which time seven buildings had been destroyed across more than 4,000 square meters.
Fire officials told reporters on Thursday that they had found evidence of cables being melted around the distribution switchboard in the main hall. They said it is highly likely that the fire was caused by short circuits.
There have been suggestions that temple's fire prevention system was flawed. They had installed thermal sensors, but the guard who noticed a heat reading assumed it was from an intruder, so he didn't take a fire extinguisher when he went to investigate. The area where the fire started didn't have smoke detectors or sprinklers.
Dignified Castle with tragic history
Shuri Castle was built about 500 years ago, when Okinawa was known as the independent Ryukyu Kingdom. It was designated a Japanese national treasure in 1933 but was destroyed by fire during World War Two. The main hall was restored in 1992, and served as the venue for a banquet during a G8 summit. Remnants of the original castle were designated a UNESCO World Heritage Site, together with the ruins of other castles of the Ryukyu Kingdom.
Challenges facing the restoration
Many locals are asking the national and prefectural governments to start restoration work as soon as possible. They say the castle was a source of their identity. "I can't end my life without seeing the castle again", sad one elderly woman who lives nearby.
That won't be easy says Iwao Yamashiro, who was involved in the first restoration. That work took more than 30 years. Yamashiro said they had no diagrams or even photos to work from. Most were destroyed during the Second World War. Yamashiro and his team interviewed local people to get as much information as they could about the building.
He says it took the concerted efforts of many experts and craftsmen to complete the job.
Kiyoshi Nakamoto was in charge of the design last time they rebuilt the castle. He says they needed long, thick timber suitable for Okinawa's climate. They had to bring them in from Taiwan back then, but that won't be possible this time, because harvesting those trees has been banned. Nakamoto says it's also going to be hard to find craftsmen with the necessary skills.
There's also the issue of financing. The 1992 work ended up costing about 7.3 billion yen, which would be worth some 67 million dollars today. But prices have changed since then, and Okinawa officials say they have no idea how much it will cost this time.
Okinawa Governor Denny Tamaki says he aims to draw up a reconstruction plan by 2022, the 50th anniversary of Okinawa's return to Japanese rule from US administration.
Japanese Prime Minister Shinzo Abe has instructed relevant ministers to secure the funds necessary to restore the castle.
They'll have at least a $3.8 million head start. That's how much people have donated so far to a fundraising campaign set up by Naha city leaders.
Masashi Kato, supervisor for the previous restoration, says the restoration work is not something you can do in a few years, but he believes the castle will one day be back.