SAN DIEGO — U.S. immigration authorities have begun flying deportees deep into Mexico in an effort to discourage them from trying to return.

U.S. Immigration and Customs Enforcement says the first of twice-weekly flights from El Paso, Texas, to Mexico City left Thursday with 133 deportees aboard, all men.

ICE spokeswoman Nicole Navas says the flights will accommodate up to 136 men and women but no children. Deportees fly from throughout the United States to Chaparral, N.M., for a short bus ride to El Paso.

The flights are not voluntary, unlike a previous program to deport Mexicans arrested by the Border Patrol during Arizona's deadly summer heat.

Under a two-month trial last year, more than 2,300 Mexicans returned on 18 flights. The U.S. and Mexico agreed in April to make the arrangement permanent.