Provincial police chief Pol Maj-General Passawarin Pongpipatpakhin led the police investigators and forensic officials to inspect the scene yesterday morning in Tambon Plabplachai of Suphan Buri’s U-Thong district, where four female and two male workers were killed in the explosion at 9pm on Thursday. Many of the deceased were found to have been burned in the accident, while firework-material debris was scattered over a 20-metre radius, he said.

Deputy provincial police chief Pol Colonel Chairat Tippayachan said Suphan Buri had less than 100 people legally permitted to manufacture fireworks, and the explosion site was not one of the licensed operators. An earlier police probe found an unnamed investor had hired the migrant workers to produce small ball – ping-pong – firecrackers at night, he said, adding that the investor had been arrested and fined for unauthorised firework production in March.

Chairat said the investor had asked the caretaker of a retired Bangkok-resident colonel’s house to use the property to accommodate the Myanmar workers, but neither the colonel nor the caretaker reportedly knew about the firework-making activity until the explosion.

Police are now hunting for the investor in question, he added.