The owners of the fireworks warehouse in Narathiwat which exploded last weekend were charged in relation to the blast upon returning to the country on Sunday.
The couple, Sompong Napol, 42, and Piyanuch Puengwirawat, 42, returned from Malaysia via the Sadao checkpoint after a court issued a warrant for their arrest in connection with the July 29 explosion in tambon Muno, Sungai Kolok district.
The blast saw 12 people killed, 121 injured and 292 houses damaged.
The couple were taken to Muang police station to acknowledge the charges, which include negligence causing deaths, importing and/or selling fireworks without a permit and violating the Emergency Decree for the Southern region, said Pol Maj Gen Anurut Eimarb, commander of Narathiwat Provincial Police.
Ms Piyanuch was also charged with expanding a building without a permit, as the warehouse was not registered with authorities, he added.
The couple will be remanded until the prosecution submits their case to the court, he said, adding they face up to 10 years in prison and a fine of up to 200,000 baht for their actions.
Separately, Chayapol Saitawee, director of the Southern Border Provinces Operation Centre (SBPOC) under the Department of Special Investigation (DSI), said the DSI is considering taking over the case, as it involves the violation of many laws, including the Hazardous Substances Act, Customs Law, the Firearms, Ammunition, Explosives and Fireworks Act and the Anti-Money Laundering Act.
The SBPOC will ask the DSI director general to invoke Section 23/1 of the Special Case Investigation Act today to launch its own investigation, Mr Chayapol said.
Asked to explain how the couple violated the Anti-Money Laundering Act, he said it would be impossible for the couple to transport such large amounts of fireworks without any authorities knowing.
SBPOC has also asked the Explosive Ordnance Disposal (EOD) unit to check if the area around the blast site contained traces of explosives not commonly used in fireworks production.
"Judging from the two huge craters at the site, I think the blast wasn't caused by fireworks alone," he said.