Mexican police say killing of a woman journalist whose decapitated body was found near the U.S. border appears to be the work of a violent drug cartel.

Police believe the victim, Marisol Marcia Castaneda was killed in retaliation for her anti-drug postings on a social media site.

Castaneda was an editor with the Nuevo Laredo newspaper Primera Hora and had posted information on a local networking site, Nuevo Laredo Live, which features a tipline to help police.

Police say a note, signed with the letter Z, likely for the Zetas Drug cartel, was left near her body warning people against posting such information.

Two other people in Nuevo Laredo were killed earlier this month because anti-drug comments they posted on the Internet.

Mexico is one the most dangerous countries for journalists.

At least ten journalists have been killed in Mexico this year.

Mexican President Felipe Calderon has deployed tens of thousands of federal police to fight against drug trafficking since taking office in 2006.

The battles have been intense around the border distribution routes into the U.S. that are sought after by rival drug gangs.