Thai authorities were investigating on Sunday a blast that killed 12 people and wounded at least 105 at one of the world's biggest petrochemical hubs.

Explosions sparked a fire at a chemical factory at the sprawling Map Ta Phut complex - Thailand's biggest industrial estate - on Saturday, forcing the evacuation of thousand of people and workers from the area in Rayong province, about 180 km (110 miles) east of Bangkok.

The Bangkok Synthetics plant, 20-percent owned by Thailand's largest industrial group, Siam Cement, produces butadiene and other raw materials used in the manufacturing of synthetic rubbers and plastic resins.

The blaze has been extinguished and many evacuees have returned home, said Verapong Chaiperm, governor of the Industrial Estate Authority of Thailand, confirming the number of dead and wounded.

"The evacuation order has been cancelled while other nearby buildings and factories around the area are under security checks," he said in an interview.

Authorities were investigating the cause of the explosions and were watching closely for the environmental impact of the spread of the chemicals, said Verapong

The plants at Map Ta Phut, home to the world's eighth-largest petrochemicals hub, have been at the centre of an environmental dispute in recent years after an environmental group said pollution from the plants had caused at least 2,000 cancer-related deaths.

A court in 2010 ruled that most of 76 industrial projects halted a year earlier because of pollution and licensing concerns could be restarted.