The public prosecution department said on Wednesday it has begun a criminal investigation into the Last Will cooperative, which claims to distribute a deadly powder to people who want to commit suicide.

The cooperative has also been ordered to halt all activities while the investigation is carried out. It is illegal in the Netherlands to help someone commit suicide and doctors may only help carry out euthanasia under strict protocols.

The cooperative hit the headlines last September with the ‘discovery’ of the deadly powder – a widely-available preservative – which is legally available. The group campaigns for the right of people to end their own lives at the time of their choosing.

Earlier this month, it emerged that a 19-year-old woman killed herself using the powder bought on the internet but her supplier is not thought to be the cooperative.

Health minister Hugo de Jonge said at the time the death was ‘extremely worrying’. The Last Will Cooperative is on the verge of operating irresponsibly and may be committing a criminal offence, he said.

In addition to the criminal investigation, the public prosecutor may also ask the courts to ban the organisation entirely, the department statement said.