BY ANDRES VIGLUCCI AND JAY WEAVER

Upping the ante in a year-long crackdown on migrant smugglers, federal prosecutors on Tuesday unveiled a dozen indictments charging 23 men with attempting to sneak scores of Cubans into South Florida by boat.

The indictments, issued in a single day by a federal grand jury in Key West, represent the biggest blow delivered to the underground migrant-smuggling industry since a federal task force last year began targeting the loosely organized criminal rings that have long operated here with relative impunity.

The cases encompass 12 separate smuggling trips that took place over the past year, including one that landed 23 Cubans on Summerland Key last month.

The other 11 operations ended with interdictions at sea by the U.S. Coast Guard -- a sign that investigators are reaping increasing success in disrupting smuggling ventures while they are underway, in part by cultivating informants who provide advance notice of trips.

''We do investigations and provide the Coast Guard information they can use in their interdictions,'' said Anthony Mangione, special agent in charge of U.S. Immigration and Customs Enforcement for Miami and a participant in the smuggling task force. ``I think we're doing pretty well in intercepting these operations. We're getting better at it, and the Coast Guard is putting a lot of resources into this. I think you will see more and more of these cases.''

NOT LINKED

Prosecutors say the 12 indictments, issued by the grand jury on April 25, are not linked, but represent typical small-scale operations that usually pay off big for the smugglers -- as much as $60,000 a trip for a boat captain, for instance. The 12 ventures carried a total of more than 200 Cubans, according to the indictments.

Investigators believe there is no major organization behind the smuggling networks, but, rather, small groups that operate here and in Cuba to coordinate the illegal crossings, Assistant U.S. Attorney George Karavetsos said.

The newest cases underscore what authorities say is the recklessness of the smugglers and the high financial stakes involved in getting their passengers to U.S. shores.

One dangerously overloaded speedboat intercepted last year carried 39 Cubans. In three instances, alleged smugglers are charged with ignoring orders to stop and leading the Coast Guard on high-speed chases in the dark that imperiled passengers.

Typically, the smugglers aren't paid until they deliver their Cuban passengers to dry land, where they are usually released and eventually receive legal residency under the Cuban Adjustment Act. If intercepted at sea, they are usually returned to Cuba.

One smuggling suspect, Orlando Magrinat, of Miami, ran his 36-foot Carrera Sport speedboat aground just off Summerland Key in the early morning of April 21 with 23 passengers on board while traveling at 40 knots to evade a pursuing Coast Guard vessel, according to a criminal affidavit. The passengers -- who all managed to reach land safely -- said they had agreed to pay $10,000 apiece for the trip from Cuba to Florida.

U.S. Border Patrol agents and Monroe County Sheriff's Office deputies found all the passengers hiding in mangroves. Magrinat was found nearly five hours after the landing, also in the mangroves. Two migrants identified Magrinat as the boat operator, according to the affidavit.

The announcement of the indictments comes a month after prosecutors unveiled eight indictments charging 18 Cuban Americans with plotting to sneak more than 200 Cubans into South Florida by boat in separate operations since 2005.

STRATEGY SHIFT

Until recently, immigrant smuggling across the Florida Straits received at best sporadic attention from prosecutors, and then typically only in cases involving deaths.

U.S. Attorney R. Alexander Acosta began targeting migrant smugglers in the fall of 2005 after several people died at sea in botched operations.

Since then, investigators say, they have learned to apply techniques used to target drug smugglers and money launderers to the migrant-smuggling rings. They also credit improved sharing of information and coordination among agencies under Homeland Security.

''You are seeing a real maturing of the agency and the operations meshing together as they're supposed to,'' ICE's Mangione said.

U.S. Coast Guard officials said there has been a dramatic upswing in migrant smuggling operations.

Coast Guard Cpt. Scott Buschman, commander of the Key West sector, said his crews tallied more than 300 go-fast boat smuggling incidents last year, up from about 200 in 2006.