Bangkok Post reported.
Responding to the blast, which woke residents and sent a plume of acrid smoke into the sky, Bangkok authorities distributed masks to thousands of nearby residents to prevent smoke inhalation.
Chaveewan Kiatchokchaikul, a spokeswoman for the operator Bangchak Petroleum, said that no injuries were reported in the blaze, which had been brought under control.
"We are investigating the cause of fire and will inform the public immediately," she said.
The company's president Anusorn Sangnimnuan also said the total damage was estimated at about 100 million baht (more than USD 3 million). He added that the damage will be covered by insurance and will not hurt the refinery’s revenue.
Meanwhile, Thailand’s Minister of Industry Phongsawat Sawatdi said that a leak in a gas pipeline could have caused the blast and subsequent blaze.
“What we need to do now is to assess the environmental impact, such as the amount of sulfur dioxide emitted and its effect on people's respiratory systems. The Natural Resources and Environment Ministry will look into these issues,” he said.
Sawatdi said the Department of Industrial Works was responsible for inspecting the safety measures to prevent the incident.
He said he would discuss plans for relocating the Bangchak oil refinery or nearby communities with Energy Minister Arak Chonlathanon.
Nearby communities should be moved 100 to 200 meters away from the fence surrounding the refinery, but there are also three or four other factories near the site, Sawatdi said.
Wednesday’s blast was the second in 18 months at the Bangchak oil refinery.
The Bangchak oil refinery, which employs around 600 people, is among Thailand’s biggest refineries with 120,000 barrels of oil processed at the site every day.
An explosion at an oil refinery in an industrial area of Bangkok has set off towering flames and sent two columns of thick black smoke into the air that could be seen across the Thai capital.
The explosion occurred at around 7.30 a.m. (0030 GMT) on Wednesday at the Bangchak refinery in the Sukhumvit Soi 64 district of Bangkok. The blast prompted the government to close an 80,000-barrel-per-day crude distillation unit at the refinery for at least 30 days,