Swiss police have arrested several people after a controversial futuristic-looking capsule designed to allow its occupant to commit suicide was used for the first time.

Police in the northern canton of Schaffhausen bordering Germany said the so-called “Sarco” capsule had been used in a wood in the municipality of Merishausen on Monday.

Prosecutors in Schaffhausen had opened criminal proceedings against several people for “inducing and aiding and abetting suicide”, a police statement said on Tuesday (local time).

Schaffhausen public prosecutor Peter Sticher told Swiss newspaper Blick that some people had been arrested “so that they were not colluding with each other or covering up evidence”.

He said the capsule’s operators knew the risks of being arrested.

“We warned them in writing. We said that if they came to Schaffhausen and used Sarco, they would face criminal consequences,” he said.

A spokesperson for the group behind the capsule, The Last Resort, said the deceased was a 64-year-old American woman who had suffered from a severely compromised immune system.

Florian Willet, co-president of The Last Resort, was among the four detainees, along with a Dutch journalist and two Swiss people, the spokesperson said. Willet was the only other person present when the woman ended her life, the spokesperson said.

In a statement issued by The Last Resort, Willet had described the death as “peaceful, fast and dignified”.

The Last Resort spokesperson said the woman had passed psychiatric evaluations prior to ending her life.

A spokesperson for prosecutors in Schaffhausen declined to give details or confirm there were four detainees.

Cast along sleek, aerodynamic lines, the Sarco causes death when its occupant releases nitrogen gas inside, lowering the amount of oxygen to lethal levels. The person is then supposed to fall asleep and die of suffocation within minutes.

The device is the brainchild of Philip Nitschke, an Australian physician famous for his work on assisted suicide since the 1990s.

Switzerland has been a magnet for advocates of assisted suicide due to laws that make it legal there.

The Last Resort said its legal advice was that the capsule could be used.

The Sarco has generated considerable media attention and discussion among authorities about whether they would allow it.

Elisabeth Baume-Schneider, the Swiss minister responsible for health, said on Monday that the capsule did not meet product safety requirements, and that its use of nitrogen was not legally compliant.

Lifeline 131 114

beyondblue 1300 224 636

-with AAP