On Friday, the office of the attorney general said in a statement it "has been made aware of concrete suspicion that political espionage has likely been conducted involving the Turkish community in Switzerland", confirming it had opened the investigation on 16 March.
The investigation follows reports that in January, two men took photos of the participants at a University of Zurich seminar discussing the 1915 Armenian genocide by Ottoman Turks, a term which the Ankara government vehemently rejects.
Turkish President Recep Tayyip Erdogan called on the United States and Britain on Thursday to drop what he said were "exaggerated" new aviation restrictions imposed on flights from some airports, including Istanbul.
Erdogan was addressing what Ankara sees as the suppression of free speech in some European Union countries because of bans put on visiting Turkish politicians, and the treatment police have meted out to their supporters.
Close to 70,000 Turkish citizens live in Switzerland, according to Swiss government statistics, while the Turkish embassy's website refers to 130,000 Turkish nationals.
Turkey's dispute with the European Union erupted earlier this month after Germany and the Netherlands blocked Turkish ministers from holding rallies to secure a "Yes" vote in the next month's referendum on expanding Turkish President Recep Tayyip Erdogan's powers. Çavuşoğlu had been scheduled to visit Switzerland for an event earlier this month, but that was canceled for lack of a venue.
Swiss prosecutors are investigating claims Turkish citizens living in Switzerland are being spied on.
Turkey is due to hold a controversial referendum next month.