UPDATE 1305 GMT: Now to the Important Question....Which Iranian official started the story of the captured troops and why?
Starting point has to be the Revolutionary Guard, given that its outlet Javan (again, not Fars, which may have repeated the story but soon deleted it) started the rumour. But with Javan soon pulling its attempted scoop and apologising, I doubt anyone will be admitting responsibility.
Indeed, Press TV brings a smile with its coverage: "Iran's Islamic Revolution Guards Corps (IRGC) rejects rumors of seven US troops being detained on the border of southeastern province of Sistan-Baluchestan."
Somehow, Press TV forgets to mention who started those rumours....
UPDATE 1225 GMT: Mystery Solved. Javan, which started the story that seven US troops had been captured, has just posted that "the news is not true" and has apologised to its readers.
UPDATE 1215 GMT: Iran's Press TV is now denying the capture of US troops who supposedly crossed into Iran from Afghanistan.
The US Embassy in Afghanistan, the International Security Assistance Force are also putting out denials.
UPDATE 1205 GMT: A Solution to the Media Mystery? Tabnak, affiliated with conservative politician Mohsen Rezaei, runs the story of seven captured US troops and two Iranians accompanying them.
The website credits Javan --- not Fars --- as the source. That is significant because Javan is affiliated with the Islamic Revolution Guards Corps.
However, I cannot find the story on Javan's website.
UPDATE 1155 GMT: The main page of the Fars website does not feature any story of the capture of Americans. Nor does the Islamic Republic News Agency, which headlines with an alleged call by Fox News for media to avoid interviewing President Ahmadinejad in New York.
No coverage on Press TV's English-language service, either, as it leads with the story of the car bombings in Baghdad.
News services are citing a story from Fars News: “Recently seven American troops were detained by Iranian guards in a southeastern province of the country ... Two Iranians accompanying the troops were also arrested.”
We are urgently checking Fars and Iranian media, as well as sources, to get details on the report.