Police have issued urgent warnings regarding a potentially lethal drug, commonly used to tranquilise animals, after it was detected at a Brisbane mail centre.

Reports suggest carfentanyl is a highly toxic, synthetic-based drug, requiring only a minute dose to cause death.

Detective Superintendent Jon Wacker of the QPS Drug and Serious Crime Group said police were very concerned to see the drug in Queensland.

"Because of its capacity to cause death, it is important we get the message out as soon as possible to the community," he said.

"The drug is based on fentanyl, but is significantly more potent.

"A small dose has the capacity to kill — this is not a drug anyone should be taking a risk with.

"Make no mistake, these are not party drugs. These are dangerous drugs and it's not a matter of if it will kill you — this drug will kill you."

Drug 'brings down elephants'

Commonly used as a tranquiliser for large animals, Queensland police warn the drug is 10,000 times more potent than morphine and should not to be used for recreational purposes.

"The drug is used as a sedative to bring down elephants or large animals," Superintendent Wacker said.

Authorities said people who came into contact with the drug on their skin and eyes were also at very great risk.

Police said the drug was being made in China and imported by recreational drug sellers across the world because of its low price and potency.

Authorities said the drug was impossible to recognise without scientific tests.

Police said more of the drug could have made it over the border into Queensland.

Police Minister Mark Ryan said Queensland police and the Australian Border Force (ABF) worked collaboratively on the importation and distribution of illicit drugs and substances, and had come together to issue a warning given the very real danger posed by this particular drug.

"I am advised that carfentanyl is a highly toxic and potent synthetic based drug, with a 0.002mg dose enough to kill a person," Mr Ryan said.

"The fact that this illegal drug has been located in Queensland is very concerning and together with the police, we are urging people to not take any risks at all with this illicit drug."