Police in northern Switzerland said Tuesday that several people have been detained and a criminal case opened in connection with the suspected death of a person in a "suicide capsule."

The "Sarco" capsule is presumably designed to allow a person sitting in a reclining seat inside to push a button that injects nitrogen gas into the sealed chamber. The person is then supposed to fall asleep and die by suffocation in a few minutes.

Exit International, an assisted suicide group based in the Netherlands, said it is behind the 3D-printed device that cost over $1 million to develop.

Swiss law allows assisted suicide so long as the person takes his or her life with no "external assistance" and those who help the person die do not do so for "any self-serving motive," according to a government website.

A law firm informed prosecutors in Schaffhausen canton that an assisted suicide involving the Sarco had taken place Monday near a forest cabin in Merishausen, regional police said in a statement. They said that "several people" were taken into custody and that prosecutors opened an investigation on suspicion of incitement and accessory to suicide.

Dutch newspaper Volkskrant reported Tuesday that police had detained one of its photographers who wanted to take pictures of the use of the Sarco. It said Schaffhausen police had indicated the photographer was being held at a police station but declined to give a further explanation.

The newspaper declined to comment further when contacted by the Associated Press.

In an email, the Dutch Foreign Ministry told the AP that it was in contact with the newspaper and Swiss officials.

"As always, we cannot interfere in the legal process of another country. At the same time, the Netherlands stands firmly for press freedom. It is very important that journalists worldwide can do their work freely," it said.

Exit International, the group behind the Sarco, said in a statement a 64-year-old woman from the U.S. Midwest — it did not specify further — who had suffered from "severe immune compromise" had died Monday afternoon near the German border using the Sarco device.

It said Florian Willet, co-president of The Last Resort, a Swiss affiliate of Exit International, was the only person present and described her death as "peaceful, fast and dignified."

Dr. Philip Nitschke, an Australian-born trained doctor behind Exit International, has previously told the AP that his organization received advice from lawyers in Switzerland that the use of the Sarco would be legal in the country.

In the Exit International statement on Tuesday, Nitschke said he was "pleased that the Sarco had performed exactly as it had been designed ... to provide an elective, non-drug, peaceful death at the time of the person's choosing."

The claims of Nitschke and Exit International could not be independently verified.

On Monday, Health Minister Elisabeth Baume-Schneider was asked in Swiss parliament about the legal conditions for the use of the Sarco capsule. She suggested its use would not be legal.

"On one hand, it does not fulfill the demands of the product safety law, and as such, must not be brought into circulation," she said. "On the other hand, the corresponding use of nitrogen is not compatible with the article on purpose in the chemicals law."

In July, Swiss newspaper Blick reported that Peter Sticher, a state prosecutor in Schaffhausen, wrote to Exit International's lawyers saying any operator of the suicide capsule could face criminal proceedings if it was used there — and any conviction could bring up to five years in prison.

Prosecutors in other Swiss regions have also indicated that the use of the suicide capsule could lead to prosecution.

Over the summer, a 54-year-old U.S. woman with multiple health ailments had planned to be the first person to use the device, but those plans were abandoned.

Switzerland is among the only countries in the world where foreigners can travel to legally end their lives and has organizations that are dedicated to helping people kill themselves. But unlike others, including the Netherlands, Switzerland does not allow euthanasia, which involves health care practitioners killing patients with a lethal injection at their request and in specific circumstances.

Some lawmakers in Switzerland have argued that the law is unclear and have sought to close what they call legal loopholes.