Photo/Illutration Shuri-jo castle in Naha on Nov. 6, almost one week after the destructive fire (Eiji Hori)

NAHA--The Oct. 31 fire that gutted much of Shuri-jo castle here was most likely caused by an electrical short circuit in the Seiden main hall, which was destroyed, according to investigators, citing scorch marks.

Okinawa prefectural police and the city fire department are focusing on faulty electrical wiring around the northeastern side of the Seiden hall.

The fire department said Nov. 6 that a short circuit was almost certainly the cause of the fire at the UNESCO World Heritage site.

The same day, the Okinawa Churashima Foundation and those involved in the management of the Shuri-jo Castle Park revealed at a news conference that two more structures were found to have been damaged in the fire, bringing the total number to nine.

According to the foundation, a security guard and some of its officials left the Seiden hall at 9:35 p.m. on Oct. 30 after pulling down shutters of the main hall. A heat detector installed inside went off at 2:34 a.m. on Oct. 31. No one had entered the main hall in the meantime.

The breaker of the main hall is automatically switched off at 9:30 p.m. each evening. The breaker was turned off as usual on Oct. 30. Only security cameras, fire alarm sensors and other devices are operated electrically after that.

Investigative sources said several scorch marks were found on electrical wiring in the main hall.

Seven security cameras were installed inside the three-story Seiden hall, but had been turned off.

Noting that the footage displayed incorrect times, investigators are trying to determine whether the cameras were turned off due to the fire or because of an electrical glitch in the Seiden hall before the blaze, the sources said.