Some suppliers of dark internet networks have voluntarily banned synthetic opioid fentanyl due to the risks it gives to users, according to the National Crime Agency.
They stopped selling it because it could lead to death and due attention to the police, one of the announcements by the NCA for Drugs, Vince O'Brien, told Observer.
Fentanyl is a recipe for the treatment of drugs, which is generally administered by doctors in the form of a patch or lollipop. It can be up to 100 times stronger than heroin and many people addicted.
Figures published in August showed that there were 75 deaths associated with him in England and Wales in 2017, an increase of 29% from 2016, when there were 58.
Mr O'Brien told the newspaper that the sale of "high-risk articles" could increase the risks for dark web providers.
He said: "There are markets that will not accept advertisements for weapons and explosives – they are the ones who will not accept advertisements for fentanyl.
"It is clear that law enforcement will give priority to supplies of weapons, explosives and fentanyl, for example, class C drugs – and that could be why they do it.
"There are also drug users on the dark network that say in the forums they do not think it's okay for people to sell fentanyl because it's dangerous and kills a lot of people."
Fentanyl for the first time has become a major problem in the UK last year and the government has vowed to fight it before it causes a deadly crisis like the one seen in the United States, where tens of thousands of deaths are attributed to opioids.
American rapper Mac Miller died of accidental overdose with cocaine, fentanyl and alcohol in September.
And sing superstar Prince died accidental overdose when he self-administered fentanyl in April 2016.