A reporter holds up an example of the amount of fentanyl that can be deadly after a news conference in Virginia, US. Credit:Jacquelyn Martin The Sunday Age has learnt that 10 people died in Melbourne in the late spring of 2015 when it is suspected a batch of heroin was mixed with fentanyl and supplied to heroin users. Among the dead were a 52-year-old man discovered unconscious in a toilet block, and a veteran drug user who had been taking heroin since he was 14. The Melbourne cluster was identified when Luke Rodda, a forensic toxicologist at the Victorian Institute of Forensic Medicine, was reviewing cases and noticed a trend. His investigations found nine people aged 25 to 57 had died with fentanyl and an element of heroin in their blood between late September and late November 2015, in two distinct areas around Richmond and Dandenong.

There was also a 10th death – the youngest on the list, a woman aged 23. Although her toxicology results did not test positive to heroin, fentanyl-laced heroin was found at the scene, supporting the theory she had taken the tainted powder. There was no evidence that any of those who died knew they were consuming fentanyl. Assistant Adjunct Professor Rodda, now chief forensic toxicologist with San Francisco's Chief Medical Examiner, said the fentanyl used in the heroin could have been extracted from legal prescription medication, but was more likely illegally produced in clandestine laboratories in China or Mexico and smuggled into the country. Commonly prescribed by doctors and used by anaesthetists, fentanyl is about 10 times stronger than heroin, meaning you need far less to create a fatal dose. In the US, it has even begun appearing in methamphetamine, cocaine and pills purporting to be painkiller oxycodone, where it is sold to unsuspecting users and consumed with often fatal results. Fake oxycodone pills that are actually fentanyl that were seized by Tennessee police. Credit:Tommy Farmer/Tennessee Bureau of Investigation via AP

Fentanyl is here, it's coming and it's killing. Fiona Patten, MP. The dark web is awash with dealers willing to sell the drug to worldwide buyers. A number of Australian-based sellers also claim to have powder fentanyl in stock and they pepper their descriptions of the product with stern warnings about its strength. One dealer offering to sell 100 milligram of pure fentanyl for $435 said the drug was only appropriate for the experienced and highly tolerant "fent" user. "This is no joke," the seller wrote. "So even opiate tolerant people are on another playing field."

Fentanyl for sale on the dark web. The Department of Immigration and Border Protection says it has detected fentanyl in international mail on 30 occasions in the past 18 months. Alarmingly, there are also emerging substances that begin to blur the line between illegal street drugs and what might be better described as chemical weapons. Australian border officials have made two detections of mammal tranquilliser carfentanil in the past year, and said although the amounts were small, a department spokeswoman said one gram equalled 50,000 lethal doses. A substance being sold as carfentanil on the dark web.

Shane Neilson, head of high risk and emerging drugs with the Australian Criminal Intelligence Commission, said the although the market for the ultra-potent drug was "very small", they were monitoring it closely due to its lethal potential. "Given its primarily legitimate purpose is to tranquillise elephants and other large animals, you can imagine the potency in the human body," he said. "Effectively there is no safe level of use of carfentanil." Mr Neilson said you didn't see "container loads or boat loads of illicit drugs" in potent opioid trafficking because "the quantities of fentanyl and carfentanil that can be lethal are measured in grams and fractions of grams". "It's a new way of looking at a potential threat."

The drugs are so strong there is fear officials and emergency service workers could be put in danger simply by coming into contact with seized packages containing the deadly powder, and a safety alert has been issued to all Australian Border Force officers. In August this year the US Drug Enforcement Administration said it found enough fentanyl in a New York apartment to kill 32 million people. The amount? Just 64 kilograms. Although the level of illegal fentanyl imports in Australia pale in comparison to the US, similarities exist between their drug markets that have experts watchful. Mr Neilson said rising prescription opioid use in Australia was a warning sign, although factors such as Australia's lack of land borders and more stringent drug prescribing practices would mean a local fentanyl problem was unlikely to reach the lethal scale seen in the US.

He said that he was aware of the cluster of deaths in Melbourne, but was cautious about commenting as there was evidence that the people who died also other had drugs in their system. Those drugs included methadone, valium, cocaine and GHB. Dr Monica Barratt from the National Drug and Alcohol Research Centre said because fentanyl was so much stronger than other opioids, users needed far less to get high, which could appeal to local drug dealers. "You might only purchase a very small amount, but it can go a long way if you were a distributor adding it to heroin or [mixing it with] an inert powder and selling it off as heroin. "It would be quite a profitable enterprise." It is also easier to smuggle in postage, she said.

In Richmond, community workers say it is important that information about drug trends is shared quickly to save lives, as a drug like fentanyl could have disastrous effects, with little warning. "Our colleagues in Canada and the US are certainly warning us to prepare ourselves for illicit fentanyl to reach our markets," said Kasey Elmore, manager of the drug program at North Richmond Community Health. "Given recent border seizures, some would argue it's not a case of if, but when." A delegation including senior Victorian police and state MP Fiona Patten recently visited cities in Canada and the US to learn about the opioid crisis. Ms Patten said many of those overdosing in those communities were not injecting drug users, but legal pain medication addicts supplied with oxycodone laced with fentanyl or carfentanil.

"I think we are doing some things that will prevent it happening as badly in Australia," Ms Patten said. "But fentanyl is here, it's coming and it's killing."