There were no reported injuries in the blast and subsequent fire, which prompted the government to close the 120,000 barrels-a-day refinery for at least 30 days.[break]
Early investigations by operator Bangchak Petroleum suggested the blast was caused by an oil or gas leak at around 7:30 am (0030 GMT), according to the company´s president Anusorn Sangnimnuan.
"There are no injuries. We assume oil or gas leaked out and somehow it caught fire," he told reporters, adding that the blaze was under control by mid-morning.
"I don´t think the cause was human error, it was caused by equipment."
Emergency services said there had been no casualties, but Bangkok authorities distributed masks to thousands of nearby residents to prevent smoke inhalation.
Responding to the blast, which woke residents and sent a plume of acrid smoke into the sky, Industry Minister Pongsawat Sawadiwat said the refinery will be shut for at least a month.
"Initially the refinery will be shut down for 30 days to investigate the cause of fire," he said, adding that health officials will check risks of respiratory damage among the local community.
The Bangchak oil refinery, which employs around 600 people, is located in a large industrial estate in a sprawling suburb.
It is among the country´s biggest refineries with 120,000 barrels of oil processed at the site every day, a company official told AFP.
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