Smoke rises from an underground fire that started two years ago in Taku, Saga Prefecture. Authorities say there is no feasible way to extinguish it at this point. (Video taken by Nami Sugiura)

TAKU, Saga Prefecture--This once-thriving mining town is paying a heavy price for its past industry: A fire started underground two years ago and is still raging out of control.

Authorities say there is no feasible way to extinguish the blaze. More ominously perhaps, the inferno, fed by accumulated coal waste and dust, appears to be spreading.

Residents say some days the fumes are noxious.

“Smoke from the underground can be suffocating. That's how it has been for the past four weeks," said Masayuki Mori, 66. "One day, I felt physically sick after walking through the area. At least, warning tapes should be set up to stop people entering the area.”

In its heyday in the early 1960s, Taku's population was around 45,000. The figure as of last August had dwindled to about 20,000. The city once boasted 14 coal mines, but they had all closed by 1972.

The fire is raging in an area known as a culm mountain, in this case a hill about 10 meters high consisting of low-quality coal scrap that accumulated from past workings. It caught fire in spring 2017 after a land owner started burning felled trees.

The fire spread underground, where there was plenty of fuel to keep it going in the form of coal scraps.

The local fire department quickly got the surface fire under control, but has had no luck with the subterranean blaze.

City authorities working with the fire department cut down all nearby trees, regularly discharge massive amounts of water in the area and keep a close watch in the hope of stopping the underground fire from spreading.

Although it is in a rural area, the culm mountain is close to downtown and the prefecture government-run Taku High School. A band of white smoke billows halfway up the mountain, giving off a pungent odor everytime the wind blows.

There have been instances of similar fires in the past, notably one at a storage yard of a cement plant in Hyogo Prefecture in 2003 and one at a culm mountain in Fukuoka Prefecture in 2017, but very few cases lasting two years, according to the National Research Institute of Fire and Disaster, a Tokyo-based organization under the central government’s Fire and Disaster Management Agency (FDMA).

The blaze raging in Taku is difficult to extinguish because it is underground. But one official believes it may be possible to control it by flooding the underground area.

The city government is now anxiously waiting to start the project because they are concerned that digging down to reach the fire could cause it to spread even further.

FDMA officials and experts in fire disaster are currently conducting field tests in the area before deciding how to move forward.