We are not sure if Mexico refers to them as "indocumentados" or "illegales" but they are being detained for walking around without papers, according to The Miami Herald:

"The number of undocumented Cubans intercepted in Mexico on their way to the U.S. border has more than doubled in the eight months since Havana eased its migration controls, according to Mexican government figures. 

The Interior Ministry numbers were the latest indication of the greatly increased flow of Cubans, both undocumented and legal, through Mexico, Central and South America and the Caribbean over the past year. 

Most, if not all of the Cubans, are heading to the United States, where they are protected from deportation to Cuba, can receive benefits as refugees and qualify for permanent U.S. residency after one year and one day. 

Interdictions in Mexico of undocumented Cubans totaled 2,300 from January to August of this year, compared to 994 in the same period in 2012, according to the Interior Ministry. 

The number does not include those who make it to the border undetected by Mexican authorities. That figure has been estimated at well over 13,000 for the 12-month period that ended Sept. 30."

To be fair, I support Mexico here. I understand that Cubans want to leave Cuba but immigration laws have to be respected. Mexico already has a problem with Central Americans who travel north to cross the US-Mexico border. 

Also, don't be surprised if Mexico is doing this with the full consent of the US, i.e. national security concerns.

At the same time, it's hard to read this article and not think about all of the nonsense that we've heard from Mexico about the US securing its border or enforcing immigration laws.

P. S. We discussed the Cuba-Mexico connection with Orestes Matacena, a Cuban filmmaker who came to the US through Mexico & follow me on Twitter @ scantojr.