The migrants were expelled by the U.S. after being denied a chance to seek asylum under a pandemic-related ban.
Guatemala is not participating in the joint campaign, said the official, who was not authorized to discuss the matter publicly and spoke on condition of anonymity.
A spokesperson for Mexico’s immigration agency said they had no information.
The U.S. Homeland Security Department confirmed last week that it had begun expelling migrants by air to Mexico under a pandemic-related authority that prevents migrants from seeking asylum at the border. Officials speaking on condition of anonymity told The Associated Press the flights include Central American families who are to be deported by Mexico to their homelands after landing.
Matthew Reynolds, the United Nations High Commissioner for Refugees representative to the United States and Caribbean, said returning asylum-seekers to their countries without proper screening for the dangers they are fleeing would violate international law.
“Individuals or families aboard those flights who may have urgent protection needs risk being sent back to the very dangers they have fled in their countries of origin in Central America without any opportunity to have those needs assessed and addressed,” Reynolds said in a statement.
The refugee agency was one of five U.N. agencies, including UNICEF, its human rights office, women's agency and the International Organization for Migration, that expressed concern for the U.S. government's continued use of the public health justification for not allowing the normal asylum process.
Natalia Lorenzo, from Guatemala’s Human Rights ombudsman office in Peten, said that on Wednesday the migrant shelter in El Ceibo was packed and she saw at least 15 Hondurans walking after being dropped off by Mexican officials at the border.
“The people are walking along the highway because they say they don’t have money to return to their country by bus,” Lorenzo said. “It’s abusive how they are just leaving them at the border.”
The U.S. Homeland Security Department, which has not responded to questions about the flights since the first one last Thursday, said the frequency of repeat crossers and transmissibility of the delta variant of the coronavirus necessitated resumption of flights to Mexico.
Daniel Berlin, deputy director of the nongovernmental organization Asylum Access, said that his organization is the largest legal services provider for asylum-seekers in Mexico, yet they have not been given any access to the people being flown into southern Mexico, despite having an office in Villahermosa where U.S. flights have landed this week.
Flying asylum-seekers to Mexico where Mexican authorities then deport them to Guatemala is unlawful, Berlin said.
“If Mexico is going to forcibly return anybody from Mexico to Guatemala, it has international obligations to ensure that the people who they are returning do not need international protection, don’t need refugee status,” Berlin said. “As far as we understand, that is not happening at all.”
For years, the U.S. government has intermittently flown deported Mexican migrants back home to make it more difficult to try to cross the border again, but this appears to be the first time it has flown Central Americans to Mexico instead of their home countries.
Biden also scrapped agreements with Central American countries for asylum-seekers to be sent there to have their claims heard, denying any prospect of settling in the United States.
Berlin said what is happening now is worse than those Trump administration agreements.
“All they’re doing is dropping people off in Peten, I mean in the jungle, at the border," he said. "So there’s not even a pretense of process. It’s just a forcible return to the poorest part of a country that in general is ill equipped to deal with these kind of protection needs.”
Repeated efforts by Biden, Vice President Kamala Harris and other top U.S. officials to discourage Central Americans from making the journey to the U.S. border have fallen flat.
July will likely mark the highest monthly count of unaccompanied children picked up by U.S. agents at the border with Mexico and the second-highest number of people arriving in families, David Shahoulian, Homeland Security assistant secretary for border and immigration policy, said in a court filing last week.
Associated Press writer Christopher Sherman in Mexico City contributed to this report.