A newspaper in the Mexican city of Monterrey has come under attack, after several armed men stormed into a branch office of the El Norte newspaper, poured gasoline and then set fire to the building.
The attack on Sunday was the third such assault to occur in the last month.
More than 15 people were working at the office in the municipality of San Pedro Garza Garcia at the time of the attack. No one was injured, the newspaper reported.
Firemen who were called to the scene quickly extinguished the fire.
"Some videos of the incident that we have in our possession show three vehicles in the headquarters located in San Pedro Avenue of the San Pedro Municipality where three people get out with a barrel of gasoline and enter the reception area and proceed to spill gasoline and light it," said Jorge Domene, a public security spokesperson.
"Fortunately there were no injuries [...] and the fire was controlled quickly. Now we have some data on the vehicles and the people," he said.
Policemen and soldiers inspected the scene to find clues in order to begin an investigation.
Sierra Madre, the office which was attacked, published a weekly supplement covering the parties and social events of local residents.
On July 10, assailants fired assault rifles and grenades at two other El Norte office in Monterrey.
Pressure from cartels
Experts say the attacks could be a sign of an escalation in efforts by drug traffickers to intimidate one of the few regional outlets that continues to cover the drug war and investigate official corruption linked to cartels, while others fall silent to intimidation.
"There are parts of the country where criminal groups decide what gets published and what doesn't," said Jose Carreno, a media expert at Mexico City's Ibero-American University.
"They're trying to extend the pressure."
El Norte is owned by Reforma, one of Mexico's biggest newspaper chains.
More than 80 Mexican journalists have been murdered since 2000, according to the National Human Rights Commission, with many of those killed reporting on crime and police.
Vowing to bring to justice the culprits behind the brazen crime, the governor of Nuevo Leon state, Rodrigo Medina, said authorities will not tolerate any attacks that curtail freedom of expression and media in the drug-ravaged state.
"We cannot allow an attack such as this on the media, whatever form of media. We cannot provoke fear for freedom of expression and freedom of the media in this case. We will get to the bottom of this to find those responsible and behind it," said Medina.
Journalists under fire
Last year, Mexico was the third deadliest country in the world for journalists after Pakistan and Iraq, according to Reporters Without Borders.
There have been more than 55,000 drug related killings and more than 6,000 disappearances during President Felipe Calderon's six-year offensive against the cartels.
President-elect Enrique Pena Nieto, who will replace Calderon in December, promises to dramatically reduce the homicide rate.
Several press freedom groups urged Mexican authorities on Monday to investigate the latest attacks.
"There is no journalist in Mexico who can feel safe when there are criminal groups who feel they can attack a national media outlet without any consequences," said Carlos Lauria, senior programme coordinator for the Americas for the New York-based Committee to Protect Journalists.
The federal Interior Department also issued a statement condemning the attack and said it has offered to help state authorities with the investigation.