Brisbane:The health authority in the Australian state of Queensland issued an alert on Tuesday, warning local communities against taking illegally sourced drugs.
The alert came after the seizure of counterfeit medications containing life-threatening substances, reports Xinhua news agency.
According to Queensland Health, tablets found in various investigations this year have tested positive to protonitazene, a very strong opioid that can be fatal even in small amounts.
The drugs have been branded to appear as genuine medications including Xanax, which is not available commercially in Australia.
John Allan, Queensland Health's Executive Director of Mental Health, Alcohol and Other Drugs Branch, urged people not to consume counterfeit or altered medications and substances under any circumstances.
He said that unsuspecting users may not notice the counterfeits, as many of the tablets appear genuine in labelled Xanax bottles.
"Protonitazene can lead to respiratory failure, loss of consciousness, coma and death, even if taken in small quantities," said Allan.
"Nitazenes, including protonitazene, are a group of synthetic opioids that can be as strong or stronger than fentanyl. They have been detected in Queensland and other states and territories in various forms including tablets, powders and liquids," he added.
The Australian Broadcasting Corporation reported that local police are trying to find the source of the illegal tablets, with an investigation ongoing over whether two deaths in the state are linked to counterfeit pills.