Video news releases are packaged news stories that usually employ actors to portray reporters who are paid by commercial or government groups.
The letters were sparked by allegations that television stations have been airing the videos as part of their news programs without telling viewers who paid for them.
FCC Commissioner Jonathan Adelstein said Tuesday the letters ask station managers for information regarding agreements between the stations and the creators of the news releases. The FCC also asked whether there was any "consideration" given to the stations in return for airing the material.
"You can't tell any more the difference between what's propaganda and what's news," Adelstein said.
The probe was sparked by a study of newsroom use of material provided by public relations firms. The study, entitled "Fake TV News: Widespread and Undisclosed," was compiled by the Center for Media and Democracy, a Madison, Wis.-based nonprofit organization that monitors the public relations industry.
When stations air video news releases, they are required to disclose to viewers "the nature, source and sponsorship of the material that they are viewing," according to the FCC.
The rules were prompted by payola scandals of the past, in which broadcasters accepted money from companies to hype their products without labeling the effort as advertising.
Diane Farsetta, senior researcher with the Center for Media and Democracy and co-author of the study, said that did not appear to be the case in the study but that "the main reason is economy. These are free stories that are given to stations that are continually under-resourced."
Farsetta said despite the publicity, stations are continuing to air releases without disclosure.
Stations that received the letters have been given 60 days to respond. If the FCC decides they have violated the rules, punishment could include fines or license revocation.