EL PASO, Texas (Border Report) — The U.S. has returned to Mexico dozens of men who were serving prison sentences for drug convictions.

On Sept. 23, Immigration and Customs Enforcement transferred 59 Mexican nationals through the Santa Teresa Port of Entry in New Mexico, according to a news release.

The inmates were all serving sentences for conspiring to possess methamphetamine with intent to distribute. Under a treaty with Mexico, they will complete their sentences in Mexico.

“The transfer of these inmates … demonstrates the robust cooperation between the United States and Mexico,” said Juan Acosta, the acting field office director for ICE’s Enforcement and Removal Operations in El Paso. “ICE is carrying out its mission by removing convicted criminal aliens from the country, and at the same time, saving taxpayer dollars by removing these individuals from our prison system.”

The 59 inmates included some who requested transfers back to Mexico. They were brought in from prisons all over the U.S. to await their removal at the La Tuna Federal Correctional Institute near the border in Vinton, Texas.

ICE removed the inmates under the 1977 Immigration and Nationality Act, which authorizes the U.S. to participate in international prisoner transfers and set the requirements of the transfer program. The United States entered into its first transfer treaty with Mexico and has since entered into 11 additional bilateral transfer agreements and two multilateral transfer conventions, which give the U.S. transfer-treaty relationships with nearly 80 countries.

ICE officials sent 41 inmates to Mexico in December.