Advocacy groups behind a so-called suicide capsule said Sunday they have suspended the process of taking applications to use it — which numbered over 370 last month — as a criminal investigation into its first use in Switzerland is completed.

The president of Switzerland-based The Last Resort, Florian Willet, is being held in pretrial detention, said the group and Exit International, an affiliate founded in Australia over a quarter century ago.

Swiss police arrested Willet and several other people following the death of an unidentified 64-year-old woman from the U.S. Midwest who on Sept. 23 became the first person to use the device, known as the “Sarco,” in a forest in the northern Schaffhausen region near the German border.