Officials have found a total of about 10,500 tonnes of carcinogenic cadmium waste illegally sourced from Tak province, and are seeking another 2,500 tonnes.
The first 2,500 tonnes were found at two foundries in Muang district of Samut Sakhon on Thursday. On Saturday about 7,000 tonnes were discovered at a warehouse in Ban Bueng district of Chon Buri. On Sunday about 1,000 tonnes were identified at a foundry in Muang district of Samut Sakhon.
Officials assumed that the cadmium tailings were sourced from a landfill in Tak province.
Industry Minister Pimphattra Wichaikul said the 1,000 tonnes found in tambon Bang Nam Jued of Samut Sakhon on Sunday were in piles, both inside and outside a foundry registered for copper melting.
During the raid that found 7,000 tonnes of cadmium waste in big bags in tambon Khlong Kiew of Ban Bueng district in Chon Buri on Saturday, police arrested a Chinese owner of an unregistered warehouse. Officials quoted him as saying that he was a middleman, bought the tailing from another Chinese man in Samut Sakhon and was waiting for resale.
The facility is among about 20 warehouses identified in Ban Bueng district, and most of them had no licences.
Cadmium has many uses, notably in the production of rechargeable batteries, pigments, metal coatings and plastics. Cadmium and its compounds are highly toxic and can cause damage to human tissues and organs when they enter the food chain. Because of this risk, its disposal is tightly regulated.
Although the cadmium waste had been neutralised before being moved to the landfill in Tak, its transportation from the landfill for melting was totally illegal.
A worker at the foundry searched in Samut Sakhon told police on Sunday that its owner gave him and his colleagues "medicine" and milk in order to protect them from contamination.
Prime Minister Srettha Thavisin said on Sunday that the discovered cadmium waste would be returned to the landfill in 15 days and scientific tests had not found any contamination in the environment.
Meanwhile, the army has prepared disaster mitigation personnel to control possible contamination from cadmium waste found at the places.