USING sophisticated methods to smuggle cocaine and to corrupt public officials, at least five major Colombian drug rings are now operating freely out of Mexico, Mexican drug experts and United States officials say. The proliferation of Colombian cocaine ``mafias'' here poses a serious challenge for the new government of President Carlos Salinas de Gortari, who has pledged to ``make life miserable for drug traffickers in Mexico.''
Not only does each group have the ability to export up to one ton of cocaine a week across the porous 1,933-mile US border. But, say US and Mexican officials, the Colombians now feel so invulnerable that they are storing huge quantities of refined cocaine in northern Mexico before funneling it to their dealers in the US.
``Mexico serves as a trampoline for Colombian cocaine,'' says Javier Coello Trejo, chief of a new narcotics-investigations unit in the attorney general's office. ``The Colombians operate mainly out of the northern states, where ... it's cheaper to transport drugs across the border.''
In October, for instance, a Mexican Army unit in Chihuahua State found 4.8 tons of Colombian cocaine stashed in a cave, making it the largest cocaine bust in Latin American history.
``It just shows the power of these [Colombian] organizations that they are willing to stockpile so much coke in Mexico,'' says a senior US drug-enforcement official. ``It means there's much more down there.... Clearly, losing a couple of tons doesn't matter too much to them anymore.''
Colombian cocaine has trickled through Mexico since the early 1970s. But Colombian groups themselves did not begin filtering into Mexico until 1986, when US law-enforcement agencies cracked down on their air and sea corridors in southern Florida.
Shifting their operations to Mexico's long, vulnerable border, Colombian traffickers took advantage of a void left by Mexican traffickers. Some Mexican drug lords had gone into hiding after a crackdown following the 1985 murder of US Drug Enforcement agent Enrique Camarena Salazar.
Mexico has quickly become a haven for Colombian traffickers. Besides offering easy land access to US markets, it has hundreds of airstrips across its northern expanse - and thousands of easily corrupted, low-paid officials.
``The Colombians love to compromise people with a badge - the higher ranked the better - so they can assure their own protection,'' an international drug expert says. ``They have successfully compromised several military units. That's their favorite target.''
With ruthless tactics and endless supplies of cash, the traffickers - all connected to either the Medell'in or Cali cartels - have turned Mexico's trickle of cocaine trafficking into a flash flood.
It's hard to pin down just how much cocaine the cartels push through Mexico, since neither production nor consumption figures are precisely known. But the DEA estimates that 35 percent of all cocaine consumed in the US comes through Mexico. As an indication of increasing volume, cocaine seizures in the US and Mexico have soared in the past three years. Meanwhile, Mexico continues to be the largest source of heroin and marijuana for the US, supplying about 40 percent of imports for both drugs.
Five years ago, DEA agents estimated that 30 tons of cocaine flowed through Mexico annually. According to Peter Reuter, an analyst of international drug trafficking at the Rand Corporation, that amount has multiplied as the Colombian cartels have shifted operations to Mexico and as Americans snort and smoke more of the snowy white powder.
Despite the increasing number of busts by both governments, cocaine traffic through Mexico is accelerating as the Colombians begin to monopolize every aspect of the drug business. Says one US official: ``The cartels now have almost total control over independent [drug] entrepreneurs here.''
For the Mexican government, which has focused its anti-drug program on stopping the production and trade of marijuana and opium poppies, cocaine trafficking is particularly baffling. There are no fields to eradicate, fewer people to catch, and more pay-off money to fight.
``We have to be more effective,'' says Mr. Coello. Part of the problem, he says, is that the ``the Colombians keep using more sophisticated methods.''
But the most significant - and elusive - source of cocaine are the undetected Colombian planes that swoop in every night in the vast northern states. To detect even the most careful traffickers, Mexico is developing a radar surveillance system on its southern border, Mexican and US sources say. The uncompleted system reflects President Salinas's commitment to combat what he considers a ``national security threat.''
Mr. Salinas has promised to purge corrupt officials and expand the power of the attorney general's office. And for the first time, he has assigned 1,000 judicial police to the sole task of combatting drug trafficking.
Even more soothing to Washington's ears is Coello's promise that Rafael Caro Quintero, a notorious Mexican drug trafficker wanted for Camarena's murder, would be sentenced by April.
But those promises are already being doubted because of Salinas's choice for attorney general: Enrique Alvarez del Castillo, an old-time politician who did little to restrain drug kingpins in his five years as Jalisco State governor. US officials say Mr. Alvarez's state police helped bungle the Camarena murder investigation.