BANGKOK, Nov. 24 (CNA) - Thailand's claim to have seized almost US$1 billion in contraband ketamine this month was wrong and tests have so far not shown up any drugs, the justice minister said on Tuesday (Nov 24).

Somsak Thepsuthin said tests which turned purple in the presence of ketamine hydrochloride reacted the same to trisodium phosphate - a chemical which can be used as a food additive and cleaning agent which is all that had been found so far.

"This was a misunderstanding that our agency must accept," he told reporters. "This wasn't a mistake. It's new knowledge."

He said testing continued. About 66 of 475 bags had been tested by Sunday.

Thailand's Office of the Narcotics Control Board had announced the seizure on Nov 12 and said that it pointed to a multinational drug network.

In medicine, ketamine is used as an anaesthetic or an anti-depressant, but as a recreational drug it is used to induce dreamy or trance-like sensations, and sometimes hallucinations.