The US Border Patrol says one of its agents rescued an infant and a toddler who were left alone by migrant smugglers in western Arizona’s Organ Pipe Cactus National Monument, AP reported.

A migrant in a group of border crossers arrested Thursday west of the Lukeville, Arizona, port of entry alerted an agent to the children’s location.

An 18-month-old was subsequently found crying and a 4-month-old was discovered face down and unresponsive. Both have received medical attention at a hospital and were released back into Border Patrol custody.

Authorities did not release any details about the children, including their genders, what country they came from and the identities of their parents or guardians.

Organ Pipe Cactus National Monument stretches along the Mexican border in southwestern Arizona, a harsh, dry landscape studded with towering cactuses and other desert flora. It’s about 130 miles (209 kilometers) southwest of Phoenix.

Because of its remoteness, the 517- square-mile (1,340 square kilometer) park is a favored crossing area for some smugglers. The human remains of suspected border crossers are often found in the area.