A woman was decapitated and her body was found in Nuevo Laredo for posts she made on social networks, according to signs found with the body Saturday.

"Nuevo Laredo en Vivo and social networking sites, I'm The Laredo Girl, and I'm here because of my reports, and yours," the message said. "For those who don't want to believe, this happened to me because of my actions, for believing in the army and the navy. Thank you for your attention, respectfully, Laredo Girl...ZZZZ."

It was the third such killing in less the two weeks. On Sept. 12, the bodies of a man and a woman were found hanging from a pedestrian overpass in Nuevo Laredo with similar messages. All three killings are believed to have been carried out by Zetas, a violent drug cartel that operates along the U.S.-Mexican border.

By Sunday afternoon, the message was clear, as several people began Tweeting and re-Tweeting the warning “"No escribais sobre los zetas" -- “Do Not write about the Zetas.”

Laredo Girl is reportedly the online name Marisol Macias Castaneda, a newsroom manager for the Nuevo Laredo newspaper Primera Hora. Her killing is significant because it was directly linked to her social networking posts, not her work at the newspaper.

As many as 74 journalists are among the more than 40,000 people believed to have been killed by the drug cartels since 2004, but the three killings this month are the first tied to social networking activities.

#Socialmedia keeping Veracruzanos alive. Who thought twitter meant public safety announcements?” Diana Enriquez posted on Twitter Sunday.

The murders of journalists have had a chilling effect, with some newspapers and television stations conceding they no longer cover the cartels for fear of retaliation. That has prompted many people to go online to post updates about the gang activities. Last week Twitter reports warned people in Veracruz that gunmen had blocked off a highway and dumped 35 bodies before police and news crews had even made it to the scene.

“These aren’t acts of political sedition or real-time attempts to bring about a change in government,” Nicholas T. Goodbody, a professor of Mexican cultural studies at Williams College, said in an interview with the New York Times. “These are people trying to navigate daily life.”

But at the same time, Mexican officials are moving to clamp down on social media use. Last week the Mexican state of Tabasco enacted a law that calls for prison time for people who share false information on the Internet. The law was enacted after a man and a woman set off a false panic saying gunmen were holding hostages at a school in Veracruz.

Despite fears that inaccurate information may cause more trouble than it prevents, many Mexicans now rely on the loose network of information shared on Twitter and blogs to know where potential danger zones are. One such source is Borderland Beat (@OVEMEX), a Twitter handle that curates and retweets many of the warnings.

“We hear explosions in the southern zone...possible risk. 11:55 pm. Be careful!” Santiago Castiello tweeted late Sunday in a post that was retweeted by Norderland Beat.