Border Patrol agents found four bodies, including three children, near the Rio Grande River in South Texas on Sunday, Hidalgo County Sheriff Eddie Guerra said.

Two of the children were infants and one was a toddler, Guerra said. A 20-year-old woman also was found, he said.

The deaths come amid a huge influx of undocumented immigrants at the Southwest border and demonstrate how treacherous it is to journey, often on foot, to the U.S. from Mexico and Central America.