GENEVA (AP) — Swiss authorities have suspended an 18-month investigation into suspected cyber-spying during international talks on Iran's nuclear program last year, saying they have turned up criminal wrongdoing but haven't found out who was behind it.

The office of Attorney General Michael Lauber says the investigation prompted by a report from Swiss intelligence authorities turned up malware "developed for the purposes of espionage" to scoop up data on many computers at a Geneva hotel. The talks in question took place at the President Wilson hotel.

Thursday's statement from Lauber's office cited evidence of criminal activity but said "it cannot be attributed to specific persons."

Kaspersky, a cybersecurity firm, announced at the time that it had uncovered the campaign, saying the malware was so sophisticated that a government must have created it.