Mexico's government says nearly 9,000 Mexicans caught as illegal migrants in Arizona have been flown to Mexico City the past two months under a voluntary repatriation program.
The Interior Department says in a Thursday statement that the migrants returned in daily flights from Tucson between July 11 and Wednesday.
The returnees took buses to their hometowns, most the poor southern states of Oaxaca, Chiapas and Guerrero.
U.S. officials say desert temperatures in the Mexico-Arizona border region soar to deadly levels in the summer, and deporting migrants to just across the border only encourages them to try again.
About 125,000 people have taken part in the repatriation program since it began in the summer of 2004.