A forest fire that started Thursday in the city of Uenohara, Yamanashi Prefecture, continued to spread Friday as firefighters and the Self-Defense Forces conducted aerial and ground firefighting operations.

As of Friday morning, the fire had burned approximately 8 hectares, according to the Uenohara Municipal Government. While no injuries or damage to buildings have been reported, the flames have advanced to within about 150 meters of the nearest residential building.

The fire was discovered Thursday morning on the 1,138-meter Mount Ogi, located in the eastern part of the prefecture and straddling Uenohara and the neighboring city of Otsuki.

The fire is located roughly 3 kilometers northwest of the Dangozaka service area on the Chuo Expressway.

According to authorities, the blaze is believed to have started near the base of the mountain along a hiking trail that includes benches and other pieces of infrastructure, before spreading upwards toward the summit and then back down toward residential areas. The cause of the fire is still unknown.

The city has issued evacuation orders to 143 residents in 76 households in the Ome district at the foot of the mountain.

Firefighting efforts continued overnight but crews were unable to fully contain the fire. Authorities ramped up their efforts early Friday morning, with helicopters from Yamanashi Prefecture, Tokyo and other nearby prefectures joined by Ground Self-Defense Force aircraft conducting water drops. Local fire departments are also battling the flames on the ground.

Authorities say the fire is being exacerbated by dry air and strong winds. The city had issued a forest fire warning on Thursday due to the lack of rainfall and low humidity.

Forest fires are more common in Japan during late winter and early spring. According to government data, more than 60% of forest fires nationwide between 2020 and 2024 occurred between February and May, when dry air, low precipitation and strong winds create favorable conditions for fires. The average burned area over the five-year period was 752 hectares, with average damage reaching approximately ?320 million.

Human-induced climate change is also making wildfires more intense. Last year, researchers in Europe determined that spring wildfires in South Korea, and Okayama and Ehime prefectures were fueled by warming and made more intense due to persistently dry soil, strong winds and unusually high temperatures.

Last February, a wildfire burned about 3,370 hectares in Ofunato, Iwate Prefecture. It was the largest wildfire recorded in Japan in roughly 60 years.

That blaze took more than a month to extinguish, involved nearly 35,000 firefighters and fire brigade members from 15 prefectures, claimed one life, damaged 226 buildings and caused more than ?10 billion in industrial losses.