Five people died in fierce firefights between suspected Gulf Cartel gunmen and Mexican troops and federal agents in Rio Bravo and Reynosa.

Those cities sit just across the Rio Grande from lucrative havens for so-called Winter Texans, setting the multi-billion dollar drug trade on a collision course with a growing tourism industry.

"We're very concerned that the Mexican military controls its violence," said Hidalgo County Judge J.D. Salinas. "I stopped going across (the border) to have lunch years back."

Salinas said he now routinely declines invitations from his counterpart in Reynosa to attend events there.

On the other hand, an average of about 18,000 passenger vehicles crossed bridges from Reynosa into Hidalgo and Pharr every day last year, according to U.S. Customs and Border Protection. More than 5,500 people walked across those bridges daily.

Miriam Medel Garcia, spokeswoman for the Mexican Consulate in McAllen, said it was too early to tell if the recent violence would affect cross-border traffic in the area.

Mexico did not see a change in southbound border crossings in the days after the shootings, but most of that weekday traffic is business related and less likely to change, Medel said.

"It doesn't matter if it (the violence) is isolated or not, Mexico is going to continue to fight organized crime," Medel said.

Cartel activity has gradually been moving east from Tijuana for nearly two decades, Hidalgo County Sheriff Lupe Trevino said. Nuevo Laredo has been plagued for years with street gunbattles and assassinations, but last week's shootouts in Reynosa and Rio Bravo were unusual.

In recent years, Laredo has begun to feel the pinch from mounting death tolls in Nuevo Laredo, as rival drug cartels battled for valuable smuggling routes. Both cities suffered the losses of retail and hospitality jobs.

Trevino said Nuevo Laredo was an example of what drug violence can do to a tourism economy. People used to make regular trips from San Antonio to Nuevo Laredo for weekend vacations. "You don't see that anymore," he said.

Even if violence becomes more regular across the river from Hidalgo County, Trevino does not expect it to spill across the border. There will always be drug-related violence on both sides of the border, he said, but cartel shootouts are unlikely in the U.S. because they are fighting for smuggling routes on the Mexican side and have more respect for American law enforcement.

But in the past two years, the killings of seven people in Laredo have been linked to rival Mexican drug cartels.

The Gulf Cartel operates violent cells of former Mexican soldiers known as the Zetas, who have been linked to killings of cartel rivals as well as Mexican public officials and are suspected in the Rio Bravo and Reynosa incidents.

"I think it's eventually going to intensify," said Rick Flores, sheriff of Laredo's Webb County. He cited the end of the marijuana harvest season when smuggling picks up and the presence of several thousand Mexican troops and federal agents sent to the border to combat the cartels after former Rio Bravo Mayor Juan Antonio Guajardo Anzaldua and five others with him were gunned down last November.

The U.S. State Department included Tamaulipas state, which stretches along the border from Nuevo Laredo to Matamoros, in a travel advisory issued in October.

Todd Huizinga, spokesman at the U.S. Consulate in Monterrey, said that the advisory remains in effect and U.S. citizens should be cautious.

In the wake of last week's violence, Rio Grande Valley residents held to distinctions in their Mexican destinations.

Sandy Combs, resort manager of Llano Grande Lake Park, an RV resort in Mercedes, said she would not think twice about visiting Nuevo Progreso, a quaint Mexican city popular with Winter Texans. Residents of her 1,134-site resort cross every day and she did not hear any voice concerns.

They go for dentist appointments or just to drink and dance, Combs said. "They love the margaritas."

But "I've lived in the Valley 26 years and you won't catch me in Reynosa or Matamoros," Combs said.

Bill Summers, president and chief executive officer of the Rio Grande Valley Partnership, said he was sitting eight miles from where Mexican agents killed three gunmen in Rio Bravo on Monday and noted he would begin to worry if the violence became regular. But avoiding certain areas, travel at night and any connection with the drug trade leave him fearless on his regular cross-border trips.

Rio Grande Valley residents cross often to Mexico to visit relatives, make doctor's appointments and fill prescriptions, so persistent Nuevo Laredo-style violence would affect this end of the valley, Summers said.

"I just don't like it close to the border," Summers said. "The border is our attraction. It's our Disney World, our theme park."