The fire started at about 6pm, and quickly spread, engulfing a building at the site as it moved.
Firefighters were soon at the scene, but were forced to battle the flames for four hours until the fire was fully under control.
No people were reported as injured in the fire, Samui District Chief Kittipop Roddon told The Phuket News this morning (Apr 23).
The fire started in an area where old rubbished had been stockpiled for years, District Chief Kittipop said.
“The area where the fire started is where garbage had been piled up for about seven to eight years. The area covers about 30 rai and has about 300,000 tonnes of household waste,” he said.
The old garbage was being bundled into standard-sized packs wrapped with rubber so be used to feed the incinerator, he explained.
“Right now we still do not know what caused of fire, which is now being investigated by Bophut Provincial Police,” Mr Kittipop said.
“No one was injured, and we cannot estimate the cost of the damage. All that was burned was old trash and one old building,” he added.
Although the flames were doused late last night, firefighters are concerned the fire might flare up again.
“The garbage on top of the piles was put out last night, but the trash buried underneath might still present a danger,” Mr Kittipop explained.
Staff at the landfill are using backhoe to access the buried trash to make sure it is still not burning, he said.
“I think it will take about one week before we can be sure the fire has been put out completely,” he added.