A car bomb exploded outside the offices of Televisa, Mexico’s largest media organization, in the early hours of Friday, local time.  The attack happened in the capital of Tamaulipas state, Ciudad Victoria, about 220 miles south of the Texas border.

Although no one was injured in the blast, according to Carlos Loret de Mola, host of Primero Noticias for Televisa on its channel Canal 2, damage was sustained on the outside of the building and the blast could be felt blocks away, with lights going out across the local area.

Posting on his Twitter account [link to: http://twitter.com/carlosloret] Loret said (translated by IPI from Spanish), “It’s not bullets anymore… It’s not grenades anymore… Now [it’s a] car bomb.”

According to Reuters no group was immediately blamed for the explosion and it was not clear what sort of explosives were used in the latest blast or how the bomb was detonated.

This is the fourth attack on offices belonging to Televisa in the past two months, with grenades thrown at offices in both the northern border town of Matamoros, also in Tamaulipas state and Monterrey, in the northeastern state of Nuevo León, over the week of 14-15 August and Televisa’s Canal 57 station in Nuevo Laredo, also in Tamaulipas state, attacked on 30 July.

In July drug cartels set off a car bomb in Mexico’s most violent city, Ciudad Juarez and another in early August in Ciudad Victoria.  The drug cartels have only recently turned to using car bombs in their increasingly lethal campaign of violence across the third most populous state in the Americas.

Following the escalation of violence and the harassment journalists have faced during the government’s attempts to crackdown on the powerful drug cartels, at least 10 journalists have been killed in Mexico this year.  Since the International Press Institute’s Death Watch began in 1997, at least 59 journalists have been killed because of their work in Mexico, making Mexico the fourth most dangerous country in the world for journalists in the past decade and the most dangerous thus far in 2010.

IPI Press Freedom Manager Anthony Mills said: “The ruthless killers of journalists in Mexico are no longer satisfied with gun attacks, kidnapping and torture. Now, they are adding car bombs to the list of brutal tactics they use to silence a media under siege. Mexico has become a war zone. Sadly, it now counts as the most dangerous country in the world for journalists.”