Mexico deported 79 percent more people from Central America's northern triangle in the first four months of 2015 than it did during the same period a year earlier, according to government statistics.
Data from Mexico's National Immigration Institute say that 51,565 immigrants from Guatemala, Honduras, and El Salvador were deported between January and April, up from 28,736, during that period in 2014.
Deportation of Guatemalans rose 124 percent, followed by Salvadorans at 79 percent and Hondurans at 40 percent.
The Inter-American Commission on Human Rights on Wednesday expressed its "concern over stepped-up actions reportedly being taken against migrant persons" that were put in place after Mexico initiated its Southern Border Plan last year under pressure from the United States.
In 2014, more than 46,000 unaccompanied minors from Central America crossed into the United States, leading the US government to turn to the governments in Mexico and Central America to try to stanch the flow.
Mexico responded with an initiative that included sending 5,000 federal police gendarmes to Chiapas, a Mexican state bordering Guatemala. More border checkpoints were opened, raids on migrants increased and authorities focused on keeping migrants off the northbound freight train known as "the Beast."
On Thursday, Adam Isacson, head of regional security at the Washington Office on Latin America, a human rights organization, said in a statement that the wave of immigration seen from Central America in 2014 continues.
"Enormous numbers of Central Americans are still fleeing, but most of them are now getting caught in Mexico instead of the United States," he said.
The countries the migrants are returned to remain extremely dangerous. Honduras and El Salvador have the highest per-capita homicide rates in the world. El Salvador is averaging 20 killings a day as the conflict between gangs, police and soldiers intensifies.
The Inter-American Commission on Human Rights said it was also worried about reports of attacks on migrant advocates in southern Mexico.
Migrant activist Ruben Figueroa in Tenosique, a town in Mexico's state of Tabasco, said police are waging a violent campaign against migrants.
"Masked officers with rifles run operations on the train to keep (migrants) off and to remove migrants from the train," Mr. Figueroa said. "They set up checkpoints on the highways, above all in the southern states of Tabasco, Oaxaca, Chiapas, and Veracruz. They enter hotels in the areas where migrants take shelter waiting for rides."
Figueroa said the flow of migrants has not decreased because conditions in their countries have not improved. He said Mexico's crackdown is only exposing migrants to greater risks of human trafficking, extortion, assault, and other crimes.
"Every day there are more people who walk, every time more exposed," he said. "Women with children walk hundreds of kilometers at night in big groups."
In Guatemala, Ursula Roldan, migration coordinator at Rafael Landivar University in Guatemala City, also raised concerns about the crackdown leading migrants to take bigger risks.
"They have changed the migration corridors," Ms. Roldan said. "The route north is changing. Maybe, too, they are beginning to use maritime routes, even more dangerous than the other migration routes."