Police are at their wit's end trying to find the producers of "k-powdered milk", a new drug cocktail which is believed to have killed seven people in Bangkok.
Pol Col Thongchai Buarangsri, superintendent of Wat Phraya Krai station, said on Wednesday police have not yet found any credible evidence which points to the producers.
The superintendent added the three other people who became sick after taking the drug could not be questioned yet, as they are still hooked to ventilators.
Last week, seven people died in Bangkok after taking k-powdered milk, also known as "k-nom pong", which experts have determined to be a combination of heroin, ketamine, methamphetamine and sleep medication.
The Bangkok South Criminal Court has issued arrest warrants for four individuals who have been charged for selling the illicit substance. They will be detained today.
Sources close to the investigation said the quartet admitted to investigators they supplied the drug which was taken by the victims. That said, they refused to say who produced the drugs or how they acquired them.
Two of the suspects were charged in relation to the deaths which occurred under Wat Phraya Krai police's jurisdiction. They were identified as Chatree Srisombat, 19, charged with selling narcotics, and Noppakao Obthom, 26 charged with narcotics possession.
The suspects were also taken to Police General Hospital for drug tests to determine if they had taken part in drug abuse, the sources said.
The other two suspects were separately charged with possessing k-powdered milk with the intent to sell in other areas -- one was arrested in Bangkok's Sai Mai district, while the other was nabbed in Pathum Thani's Lam Luk Ka district.
Police determined they were not linked to the suspects arrested by Wat Phraya Krai police, a source said.
The suspect arrested in Sai Mai district, identified as Ratthanachoke "Jim" Kiratichote, 21, told police he bought the drugs from a woman in Sai Mai for 470 baht per gramme. He had planned to resell it for 600 baht a gramme, police said.
At a briefing at Government House on Wednesday, Prime Minister Prayut Chan-o-cha said the only way to curb the drug trade is by cutting demand for illicit drugs.
"As long as there is a demand for drugs, someone will attempt to smuggle and/or produce them," he said.
Gen Prayut called on families to keep their children as far away from illegal substances as possible while urging communities to help the government by looking out for and reporting suspected drug trafficking activities.
The government will investigate the transactions of those involved in drug cases to track down traffickers and seize their assets, he added.
The prime minister also asked the public to notify him of any drug dealing activity in their areas, if the police have done nothing to deal with it.
At the Institute of Forensic Medicine on Wednesday, the mother of Withun Phuthong, who died after using k-powdered milk in Bangkok's Klong Toey area, collected his son's body for funeral rites.
The mother said she found her son lying face-down near their house after attending a party on Dec 10. He appeared to be drunk and had fallen asleep, she said.
He was not breathing when she found him at around 3pm. He was pronounced dead later at the hospital, she said.