Preliminary investigations showed that the samples collected a week ago from the affected tanks were still deadly.
"Tests carried out at the quarantine unit showed that fish could not survive when they came into contact with the chemical contained in the water sample collected from the affected tanks."
"The chemical also had a strong petroleum smell," he said when contacted on Wednesday.
Fish at UWL died last Monday.
The Department of Environment (DOE) had cautioned UWL against draining the affected water weighing more than 70 tonnes until further notice.
Deadly chemical cause of fish deaths
MALAYSIA - The chemical used to poison 600 fish at Underwater World Langkawi (UWL) recently is deadly, state Fisheries Department director Sani Mohd Isa said.