Iran's official news agency, IRNA, reports three detained U.S. citizens have been charged with espionage.
Tehran's general prosecutor, Abbas Jafari Dolatabadi, said Monday a final decision about the detainees would soon be announced. He added that investigations are continuing.
The three Americans were detained on July 31 for entering Iran illegally, after they apparently strayed across the border while on a hike in northern Iraq.
Speaking in Berlin Monday, U.S. Secretary of State Hillary Clinton said Washington believes there is no evidence to support any charge whatsoever. She again appealed to Iranian authorities to exercise compassion and release the trio.
Last week, the detainees' families said Shane Bauer, Sarah Shourd and Josh Fattal have had two consular visits with Swiss diplomats at Evin prison in Tehran. The first visit was in September and the second was last Thursday. Switzerland represents U.S. interests in Iran.
The families say the hikers are in good physical shape.