(CNN) -- Mexican authorities have rescued six undocumented Cuban migrants who had been held for ransom for a month in Cancun, a vacation hotspot on the nation's Yucatan Peninsula, the state-run Notimex news agency reported Wednesday.
The abductors, who were not apprehended in Tuesday night's rescue, were seeking between $8,000 and $10,000 from relatives in Florida for each of the five men and one woman they had been holding in a series of safe houses, Notimex said.
The Cubans said they arrived in Cancun on a raft and were picked up from the streets of Cancun by men in a pickup truck, the news service said.
The Yucatan Peninsula, particularly the municipalities of Cancun, Isla Mujeres and Cozumel, is a major landing point for smugglers who bring Cubans into Mexico and take them to the U.S. border.
"It's a major receiving dock for things coming from the Caribbean," said Samuel Logan, founding director of Southern Pulse, an online information network focused on Latin America. "It's a pretty important reception point."
Human smugglers charge up to $10,000 per person to transport them by boat from Cuba, usually from the westernmost province of Pinar del Rios, and then overland in Mexico to the U.S. border.
Mexican and Cuban officials estimate that up to 10,000 Cubans are smuggled into Mexico each year, the online Diario de Cuba publication said Wednesday.
The Cancun area has become more popular with human smugglers in the past decade because the 135-mile-wide Yucatan Channel is not heavily patrolled by the U.S. Coast Guard as other parts of the Caribbean Sea. Most U.S. interdiction efforts occur in the Straits of Florida between Cuba and Florida.
Cuban smugglers have been working with drug-trafficking organizations in the Yucatan area, particularly the Beltran-Leyva and Zetas cartels, authorities say. Lately, officials say, the Cuban smugglers have been branching out into trafficking cocaine from Colombia.
The Noticaribe online publication said in November that a group of Cuban migrants had reported being tortured in Cancun by abductors who demanded $10,000 from family in Miami, Florida.
Of the 34 killings in the Cancun area in 2007, Noticaribe said, many of them were Cubans involved in human trafficking.
Tuesday's rescue of the six Cubans came one week after Mexican authorities discovered the bodies of 72 migrants from Central and South America on a ranch in Tamaulipas state. Officials are investigating whether the Zetas cartel killed the migrants and for what reason. It's possible the migrants refused to work for the cartel or were unable to obtain ransom money.
"Sometimes the Mexican organized crime group says, 'The hell with it. We're not going to deal with these people,' and they kill them all," Logan said.
Elements from the Mexican navy, army and state and local police made Tuesday's rescue of the six Cubans after authorities received a telephone tip. The hostages said they were guarded at their last house by three abductors, two Mexicans and a Cuban.
The Cubans ranged in age from 22 to 46 years old, Notimex said, and were identified as Lazaro Hernandez Albeja, Eusebio Galaz Sabrino, Dandy Acosta, Edel Eime Gama, Daniel Cardo Rodriguez and Suramy Acosta Camber.
In Mexico, human smuggling is a $15 billion- to $20 billion-a-year endeavor, second only to drug trafficking, Logan said.
That money, which used to go mostly to smugglers, now also flows into the hands of drug cartel members.
The drug-trafficking organizations charge the smugglers a price per person for the right to cross over their territory, a practice called "derecho de piso," or right of passage. Or they often abduct the migrants and hold them for ransom.
The Center for Strategic and International Studies, a bipartisan, nonprofit policy institute based in Washington, noted in an August report that human smuggling and other illegal activities are playing an increasingly important role as narcotraffickers diversify their activities.
"The drug cartels have not confined themselves to selling narcotics," the report said. "They engage in kidnapping for ransom, extortion, human smuggling and other crimes to augment their incomes."
Some cartels have come to rely more in recent years on human smuggling.
"For the Zetas, it's been one of their main revenue streams for years," Logan said about the vicious cartel, which operates mostly in northeastern Mexico.