The state general attorney's office said it does not have any information about the fliers threatening Courage for Tamaulipas.
The agency added that it does not have a protocol for protecting residents in situations like this because it is the first of its kind.
A survey by Freedom House of Mexican journalists and bloggers showed that 96% of respondents know a colleague who has been attacked. The organization surveyed 102 journalists in 20 Mexican states.
Freedom House published a report, Digital and Mobile Security for Mexican Journalists and Bloggers, which cites a September 2011 incident where two people were found hanging from a bridge in Nuevo Laredo.
"A message left near the bodies warned that the same thing could happen to any internet user who crossed that criminal organization. Those murders were followed by the killing of a journalist using the nickname "la Nena de Laredo" who had posted entries against criminal activity on Nuevo Laredo en Vivo, a social media forum," the report said.
Following these crimes, the administrator of Courage for Tamaulipas published a message condemning the incidents and affirming that "innumerable" citizens continue to resist against organized crime's grip.