The Ministry of Industry is investigating the disappearance of more than 10,000 tonnes of cadmium tailings stored at a smelting factory in Samut Sakhon.
The probe comes after Industry Minister Pimphattra Wichaikul led a team of officials to inspect the factory where the carcinogenic cadmium waste was stored.
Ms Pimphattra said that a check found 2,440 tonnes of cadmium tailings were packed in large bags.
But the minister said the figures do not match the 13,450 tonnes shown in a document submitted by a company in Tak seeking permission from the Tak industry office in August last year to transport them to Samut Sakhon.
"The industry office and relevant agencies were instructed to investigate where the missing 10,000 plus tonnes are," she said.
Ms Pimphattra also said she told the permanent secretary for industry to set up an inquiry panel to look into the mishandling of the cadmium tailings in the two provinces.
The chief of the Tak industry office, Napat Techasiripat, has been transferred to work at the ministry pending the probe, she said.
Ms Pimphattra said she has also ordered the tailings from the factory in Samut Sakhon to be transported back to the northern province of Tak within seven days and buried in a landfill within 15 days.
The Central Investigation Bureau (CIB) has warned that the mishandled cadmium tailings in two provinces may be hazardous because it is in the form of dust and could easily contaminate the environment.
CIB commissioner Pol Lt Gen Jirabhop Bhuridej said on Friday that the mishandled cadmium waste was found in big bags at a smelting factory off Ekachai Road in Muang district of Samut Sakhon.
It is unclear if the amount found equals or nears the 11,010 tonnes that are unaccounted for.
Pol Lt Gen Jirabhop said the CIB's Natural Resources and Environmental Crime Suppression Division (NED) earlier found that the carcinogenic waste had been illegally transported from its landfill in Tak province to Samut Sakhon.
Provincial authorities were also asked to take action against Bound & Beyond Plc in Tak and J & B Metal Co in Samut Sakhon, said the CIB commissioner.
The cadmium waste detected in the two provinces was in the form of dust. If exposed to rain or water, it would seep into the ground and become a carcinogen, a substance that could cause cancer.
It would affect long-term health if people consumed contaminated food or inhaled it, said Pol Lt Gen Jirabhop.
The NED found that several bags of the cadmium waste were torn, and there were traces of car tyre marks on them.
He said it was necessary to immediately declare the areas as disaster zones because the tyres would be contaminated with the toxic substance.
The cadmium waste is now being examined by experts to confirm whether it was a serious life-threatening substance or not, said Pol Lt Gen Jirabhop.
Sonthi Kotchawat, a health and environment expert, posted on Facebook that the cadmium tailings had already been buried in a landfill in Tak and questioned why the industry office in Tak gave permission for the ore tailings to be exhumed for recycling.
He cited an environmental impact assessment report from the factory in Tak which states that industrial tailings are hazardous and must be buried in a landfill permanently.
Samut Sakhon governor Phon Damtham on Friday declared the smelting factory in Samut Sakhon's Muang district and the surrounding area off-limits to people for 90 days after the cadmium tailings were found stored there without permission.
Mr Napat, the chief of the Tak industry office, said that the office had given permission for the ore tailings to be transported to Samut Sakhon in line with criteria set by the Department of Industrial Works.
The factory in Samut Sakhon also has a proper licence to operate, he said.