MIAMI — THE diesel-throated growl of ''cigarette'' boats snaking through the Florida Keys at night was once a familiar sound to federal agents here. Speedboats were a basic tool of cocaine smugglers in the early '80s.
Then, thanks to concerted law enforcement pressure, Colombian narcotraffickers shifted the bulk of their trading routes west to Mexico. But now the waters off south Florida are looking like reruns of ''Miami Vice.''
While experts disagree over why speedboats are back in vogue, their return is indicative of the enduringly amorphous and increasingly businesslike nature of this illicit industry. Despite cutbacks in interdiction efforts by the Clinton administration, investigations and arrests continue in Miami, providing clues into how Colombia's Cali cartel has managed to thrive in south Florida.
The arrests of three key Cali cartel leaders last year prompted the head of the US Drug Enforcement Administration, Thomas Constantine, to declare that a ''mortal blow'' had been struck against the ''unholy trinity who lead the Cali mafia.''
But one drug lord has since escaped. And federal agents here say the Cali network in Florida appears unshaken, indicating that subordinates have assumed their leaders' responsibilities.
After the demise of the Medellin cartel in the early 1990s, the supposedly less violent and more businesslike Cali cartel acquired an 80 percent share of the cocaine flowing into the United States.
''The trafficker of the '90s is much more sophisticated, and probably more well-educated, a person that is well-schooled in the concept of operations and what [rules] he has to follow,'' says James Milford, head of the DEA's Miami field office, which is staffed by more than 350 agents.
Miami functions as what Mr. Milford calls one of the cartel's key ''command and control centers.''
Cartel operatives here coordinate transactions in different parts of the United States and abroad using the same tools, federal agents say, any modern-day international executive uses - cellular phones, fax machines, and beepers.
''It's a region they know, it's people they know, it's trusted contacts, it's all the sort of things that any businessman would like to feel comfortable doing his job,'' says US Customs Service spokesman Michael Sheehan.
For example, last month DEA agents arrested a suspected Cali cartel ''manager'' who had been working out of a house in an affluent Miami neighborhood. He had coordinated the pickup of nearly 1,300 kilograms (2,860 pounds) of cocaine by his associates in Houston. He had arranged for another group of partners to transport the narcotics to New York.
Another Cali cartel manager was arrested recently in a suburb north of Miami. He arranged cocaine shipments from Colombia to western Europe.
In another raid in Miami last month, DEA agents seized $13 million of cocaine from a suspected Cali cartel warehouse. The plastic-wrapped boxes bore the markings of different groups within the Cali cartel, Milford says, a sign that traffickers have adopted yet another sound business practice: the pooling of resources.
While the managerial skills of Miami-based traffickers have grown more sophisticated, the handling of their cash flow has become cruder, in some instances.
DEA agents have found that the cash profits are shipped back to Colombia the same way they get the drug into Florida - in bulk containers dropped from a plane or hidden on cargo ships. Mr. Milford attributes this change to tougher banking regulations and a crackdown on drug money- laundering.
AS for the return to using speedboats, US Customs agents say it indicates that inroads are being made in the traffickers clandestine corporate structure.
They are ''off-balance and not able to go through their more normal systems, like hiding the drugs within international cargo, comingling it with legitimate cargo entering the US, which takes a great deal of coordination ... a much broader network of individuals,'' says Mr. Sheehan.
But other experts say that speedboats are being employed because more shipments are being dropped off in Cuban waters. The boats ''can go much faster than the Cuban Coast Guard or the Cuban Navy,'' says Bruce Bagley, an expert on the illegal drug trade at Miami University. Speedboats then run the contraband to the Florida Keys or other stretches of the south Florida coast.
As the US-Mexican border has been tightened up and as Mexican traffickers have taken over the cocaine trade on their own territory, the Cali cartel has shifted its delivery routes back to the Caribbean, according to Mr. Bagley. ''There's a kind of subdivision of the United States taking place, with the [Mexican traffickers] increasingly important out West, particularly in the Southwest, and the Cali cartel dominating east of the Mississippi.''