One person is dead and multiple people have been rushed to hospital following a deadly drug mix-up in Victoria.

The state’s health department issued an alert on Wednesday after heroin was found in other illegal drugs.

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The victims thought they were using cocaine or methamphetamine, but specialised blood tests later revealed heroin may have been mixed into the drugs.

There have been four separate incidents, including the death, across the state.

The alert from Victorian authorities details the “very different” effects the substances have.

“Opioids are central nervous system depressants, typically producing a range of effects including pain relief, sedation and respiratory depression (dangerously slow breathing),” the health department’s alert said.

“Small amounts of opioids can cause life-threatening overdose, especially in people who have never used opioids or only use them occasionally.

“Cocaine and methamphetamine produce stimulant effects, whereas heroin produces sedative effects and can lead to life-threatening overdose.”

The health department urged users to be aware of the signs of opioid overdose and carry naloxone, a life-saving medication that could help reverse a reaction.

More information about the risks of the drugs can be found here.