(CNN) The Department of Homeland Security plans to bus migrants from Tucson, Arizona, to El Paso, Texas, in an expansion of its controversial program to return migrants to Mexico to wait for their US immigration proceedings, according to two officials.

Migrants would be taken more than 300 miles from where they initially crossed the border, and eventually returned to Mexico from El Paso. The Washington Post first reported the expansion to Tuscon.

There is already infrastructure in place in El Paso for managing the returns, according to a DHS official. At the moment, Tucson doesn't have the capacity to carry out what is known as the "Remain in Mexico" or Migrant Protection Protocols program.

Roughly 60,000 migrants have been returned to Mexico since the program's inception last January.

Officials have previously said that returns to Mexico would be expanded border wide. Tucson was one of the last areas without a program to send migrants back to Mexico.

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