Rumors fly quickly after an unsolved slaying, so it is little surprise that many here believe the shooting late last month of a columnist for a small weekly newspaper actually was a warning to its high-profile publisher.

The publisher, Jesus Blancornelas, was nearly killed seven years ago when hit men for a drug cartel shot him as he sat in his car. And it was Blancornelas, not the columnist, who wrote most vociferously about alleged connections between the cartel, certain politicians and police departments.

Even though Blancornelas said the June 22 slaying in Tijuana of Francisco Ortiz, a co-founder of the weekly Zeta, will not muzzle him, the shooting was seen as a warning to all Mexican journalists who dare to criticize drug trafficking. They are an increasing number, spurred by a growing ambition among Mexico’s press to investigate corruption and crime.

The slaying “certainly has put us on edge,” said Raul Ruiz Castillo, news director of Frontera, a Tijuana daily. “The situation with drug trafficking has forced us to pull back at times, to be more careful in what we write about and what photos we publish.”

Ortiz, 48, was shot four times after getting into his car. His two children, ages 8 and 10, were in the car but were unhurt.

According to the Inter American Press Association in Miami, Ortiz is the fifth Mexican journalist killed since 2001. All worked for newspapers in border cities. In total, 39 Mexican journalists have been killed in the past 15 years, according to the press association.

Roberto Mora, an editor of El Manana newspaper in Nuevo Laredo, was stabbed to death in March. Human-rights advocates said the killing was likely due to his writing that linked drug traffickers and corrupt officials.

“Drug trafficking has begun to seep into all aspects of life here, and for that reason it’s more difficult to be a journalist on the border than anywhere else in Mexico,” said Jorge Santibanez, president of El Colegio de la Frontera Norte in Tijuana. “Other newspapers report on captures, trials and drug seizures, but Zeta does analysis and investigations that are not typical of most newspapers here or anywhere.”

For much of Zeta’s 24-year history, Blancornelas, 68, and his staff have endured death threats and attacks. The weekly is devoted, in part, to the memory of Blancornelas’ close friend and Zeta co-founder, Hector Felix Miranda, who was killed in 1988 by masked gunmen.

Ortiz recently had joined a task force with members of the Mexican government and the Inter American Press Association, a non-profit organization that works on press issues throughout the Americas. The task force was due to reopen an investigation into Felix Miranda’s death. It also was to investigate the 1991 fatal stabbing of Victor Manuel Oropeza, a columnist for the Diario de Juarez.

Since the Felix Miranda killing, Zeta has published numerous articles alleging that the slaying was ordered by Jorge Hank Rhon, a Tijuana businessman whose father was among the most powerful in the 71-year reign of Mexico’s Institutional Revolutionary Party, or PRI.

Hank Rhon, the PRI candidate for mayor of Tijuana, has repeatedly denied any involvement in either the Felix Miranda or Ortiz slayings.

Zeta is known throughout Mexico’s journalism community as a trailblazer.

“For many years, Zeta was the only newspaper writing about corruption and drug money among the police and judicial system,” said Ricardo Trotti, director of the Inter American Press Association. “There is a special situation on the Mexican side of the border . . . where mafias have great power and doing journalism becomes very risky.”

But within Mexico’s evolving press, Blancornelas and his staff have also made adversaries among competing publications that view the 48-page tabloid as prone to yellow journalism.

“Zeta has done a lot of important work, and for that they should be applauded,” said Dora Elena Cortes, a longtime city reporter for the national newspaper El Universal, who recently launched an independent news agency. “But Zeta’s view is they do good work and the rest of the press is corrupt. Well, Mexico’s press is changing. There are more editors and reporters now who are writing about drug trafficking and government corruption.”

Blancornelas and Felix Miranda launched a weekly, ABC, in 1977 and soon were threatened with arrest after writing that the Baja California state government was riddled with corruption. To avoid prison, both men fled to San Diego.

In 1980 the allegations against them were dropped, and they revived the weekly as Zeta, for the last letter of the Spanish alphabet.

Soon afterward, they returned to Tijuana. But Zeta was never embraced by the rest of the local or national press.

“They don’t practice quality journalism with attributed sources, etc., but Zeta has become a symbol of committed journalism, and that’s important for Mexico,” Trotti said.

The development of a more independent and critical press in Mexico has largely been pushed by cataclysmic social events. The 1985 earthquake in Mexico City, the 1994 Zapatista uprising and the 1995 peso crash prompted journalists to look harder at their government and how public money was spent.

The defeat four years ago of PRI also reinforced journalists’ aspirations. Now, Trotti said, such papers as Monterrey’s El Norte and its Mexico City sister publication, Reforma, are training their reporters to go well beyond copying government press releases.

Tijuana’s Frontera, part of a chain of northwestern Mexican dailies owned by Healy Media Inc., is another example of newspapers criticizing local affairs and supporting themselves through non-government advertising, Trotti said.

Diana Washington Valdez, a reporter for Texas’ El Paso Times, has spent much of her career working alongside Mexican journalists. For years, she wondered why her colleagues weren’t more aggressive.

But in the course of covering the dozens of unsolved murders of young women across the border in Ciudad Juarez, Valdez said she began to empathize with the problems confronted by Mexican reporters who dare to delve into the impact of drug money and organized crime.

“They live and work under very different conditions that can be very dangerous,” said Valdez, who recently completed a book on the murders called “Harvest of Women: A Mexican Safari.”

“When it comes to writing about the women’s murders, perhaps we’re in a better position to do it.”

One Mexican newspaper that accused government and police officials of not properly investigating the murders is Norte de Ciudad Juarez.

Alfredo Quijano, editor of the 25,000-circulation daily, said he and his reporters often receive threats by telephone, in the mail or on the street.

They also are often hauled into court to answer police questions about articles they have written.

“We not only have to deal with pressure from drug traffickers but also pressure from the government and the police,” Quijano said. “This is something that happens all up and down the border.”

Since the Ortiz murder, Blancornelas has all but gone into hiding, refusing to speak with journalists. Outside the newspaper’s offices, located in a house in a middle-class neighborhood, a dozen men, some carrying automatic rifles, stand guard.

Blancornelas never goes anywhere without them.