The vast majority of Cubans sneaking off the island now enter the US through Mexico after US relatives pay thousands of dollars to organized crime networks that scoop them off Cuba's westernmost tip in souped-up speedboats.
The Mexico route is more dangerous than a direct, 145km voyage from Cuba to Florida, but there is less chance the US Coast Guard will intervene. Nearly 90 percent of all undocumented Cubans who make it to the US now come overland rather than reaching US shores by boat, US Customs and Border Protection say.
From the Mexican coast, Cubans then travel up to the US border, where unlike other undocumented migrants, they are welcomed in under US law.
Mexico, already struggling against organized crime, is paying the price for the migration shift, especially in Cancun, the nation's glittering Caribbean getaway. On Monday, investigators there found the body of a Cuban-American from Miami, Luis Lazaro Lara Morejon, handcuffed and with duct tape over his eyes. He had been shot 10 times, obliterating his face.
Days earlier, authorities had arrested at least eight people on suspicion of smuggling Cubans to Mexico, including six Cubans with US residency or citizenship who had just been interviewed by US authorities. Lara had connections to the suspects, Mexican officials say.
"These gangs are well-organized, well-financed and very powerful," said Senator Carlos Navarrete, who was among a group of Mexican lawmakers who came to Havana to discuss the issue with Cuban lawmakers in June. "They are a very serious problem for both governments -- Cuba and Mexico."
Some 9,296 Cubans arrived in the US from Mexico between Oct. 1 and July 22, more than double the 4,589 who crossed or were picked up by the Coast Guard in the Florida Straits during the same period.
The Mexico route is now so popular that US immigration officials call those who follow it "dusty foot" Cubans, a play on Washington's "wet-foot/dry-foot" policy that lets Cuban migrants captured on US soil stay in the US, but sends those picked up at sea back to the island.
Mexican officials blame increased security along the US coast, but the US official said richer and more powerful smuggling gangs are responsible.
Cuban authorities are barred from using force to stop the boats, except in self-defense. Instead, they contact the US Coast Guard with the fleeing vessel's coordinates -- even if it is clearly headed to Mexico. And since combating people-smuggling between Cuba and Mexico is not a top Coast Guard priority, US officials generally just notify the Mexican navy.
Detentions of undocumented Cubans in Mexico have soared from 254 in 2002 to 2,205 last year, according to Mexico's National Immigration Institute. But most are released after 90 days at immigration centers. Only 722 Cubans -- one third of all those arrested last year -- were repatriated to Cuba.
The rest make their way to the US border, where entering Cubans rose from 6,130 in fiscal 2004 to 7,281 in 2005 and 8,677 last fiscal year, which ended on Sept. 30.