One summer night last year, state police raced through the downtown streets here in a shootout with alleged kidnappers just a few blocks from the international bridge that connects the city with El Paso.

At the end of the high-speed gun battle, Chihuahua state police caught their suspects, who included three Mexican army soldiers belonging to a special federal police force sent to the border to combat drug-related kidnappings and other violence.

The confrontation was not an isolated incident in this sprawling desert border city where violence is rampant, and citizens say they routinely find police on either side of the law.

"Everyone in Juarez knows the police work for the drug traffickers and that they kidnap and kill people," said Alfredo Quijano, an editor for the Ciudad Juarez edition of the Monterrey daily newspaper, El Norte. "But government authorities haven't done anything about it."

Mexican officials argue they are not entirely to blame.

"As long as Juarez shares a border with the largest drug consuming nation in the world, our city will be a conduit for the drug trade," said municipal police chief, Javier Benavides. "This creates a set of very difficult problems for us."

The seamy side of Ciudad Juarez surfaced again last week when Mexican and U.S. law enforcement authorities discovered isolated desert grave sites allegedly containing as many as 100 murder victims. After a week of intensive digging, officials said they have found the remains of six people believed to have been shot or suffocated.

But Ciudad Juarez, crowded against the border of western Texas, is a city of extraordinary contrasts, a crossroads for both the best and the worst of modern-day Mexico. The same proximity to the United States that has made it one of the hemisphere's biggest gateways for illegal narcotics and immigrants has also made it one of the country's premier locations for industry and U.S.-operated assembly plants that depend on cheap labor.

The border geography that is cursed for attracting Mexico's most powerful drug mafia, the Juarez cartel, is embraced for drawing assembly lines of Ford Motor Co., General Electric Co. and other leading U.S. firms that helped pull Mexico out of a crushing economic crisis.

Ciudad Juarez claims ostentatious mansions that could dwarf houses in wealthy American suburbs, and vast slums built of cardboard and plywood packing crates. Huge modern factories framed by lawns kept lush by whirring sprinklers loom beside dusty shantytowns without running water. Eight-lane boulevards connect the assembly plants to the airport and main highways, but in most factory workers' neighborhoods the streets are little more than narrow dirt paths impassable to most automobiles.

According to criminologists and sociologists, this volatile mix of wealth and poverty, legitimate and illegal businesses, has contributed to Ciudad Juarez's status as one of the most violent and corrupt cities in Mexico.

"Migratory patterns in almost any other Mexican border city are different than those in Ciudad Juarez," said Teresa Almada, a sociologist and director of the CASA youth center, which offers support programs for new migrants. "People come here to stay, not necessarily to go to the U.S. Such an intense flow of migration means the population is more vulnerable and stripped of its social fiber."

Now, along with the major drug trafficking organizations that base their operations here, there has been a proliferation of an estimated 800 neighborhood gangs, according to Jose Antonio Parra, a criminologist. With an estimated population of 1.5 million, the city recorded 242 homicides last year.

An entry-level municipal police officer makes just under $500 a month, and federal officers are paid only slightly more, making them easy targets for drug traffickers offering thousands of dollars or more a month to protect their shipments, according to Mexican police officials.

Five police agencies answerable to different bosses have jurisdiction in Ciudad Juarez. "There has been friction between the agents, especially when the [federal] judicial police do not want to identify themselves," city police chief Benavides acknowledged. "When authorities assume responsibilities that do not correspond to them, it definitely creates tensions."

In addition to natural rivalries, tensions have flared in recent years between police units protecting rival drug trafficking gangs.

"In many cases it was not clear . . . if the authorities were working with the goal of fighting drug trafficking in general, or were in the employ of a drug trafficker looking to weaken a rival gang," the human rights group Americas Watch wrote in a report on police corruption in Mexico.

Those reports, along with accounts of witnesses, have led human rights groups and families of an estimated 200 people from the Ciudad Juarez-El Paso area who have disappeared in recent years, to believe that law enforcement authorities have been involved in many of the disappearances.

U.S. FBI officials said an informant who led them to the grave where the remains of the six bodies were found last week was a former police official who witnessed the burials.

Until the recent investigation, neither U.S. nor Mexican law enforcement agencies showed much interest in probing the disappearences, according to family members.

"We're not talking about ordinary citizens disappearing here," Chihuahua state attorney general Arturo Gonzalez Rascon said in an interview last week. "We're talking about people who were involved in drug trafficking and who were involved in activities that have certain kinds of consequences. So they disappeared."

That attitude angers many people, including Alberto Medrano Villarreal, president of the city bar association and an attorney for the families of some of the missing victims: "You can't justify violence like that--in a just society you just can't cover up executions."

Yet the geography of Ciudad Juarez seems well suited for hiding crimes. The urban area is surrounded by sparsely populated desert lands that have long served as dumping grounds for homicide victims. Even the small ranch where six bodies were unearthed last week has been under suspicion for several years.

"We've been publishing articles calling that ranch a narco-bunker since 1996," said newspaper editor Quijano. "Those properties are like narco-barricades, surrounded by huge fences and razor wire. You hear witnesses talking about trucks entering the property full of people, and trucks leaving the property with, well, fewer people. Ranches like that are dotted all over the outskirts of Juarez."

Researcher Garance Burke in Mexico City contributed to this report.

CAPTION: Police enter a ranch in northern Mexico where six sets of remains have been found. The news did not surprise residents of Ciudad Juarez, where violence has become commonplace.