U.S. Border Patrol agents were desperately searching Wednesday for a missing 2-year-old girl whose mother lost track of her while the two were trying to cross the Rio Grande River and illegally enter the United States.

The girl's mother, from Haiti, was detained by border agents Monday. The Del Rio Border Patrol Station in Texas said the mother told them she crossed the river into the U.S. from Mexico, and couldn't find her daughter — a Brazilian national — while crossing.

4 BODIES, INCLUDING 2 INFANTS, DISCOVERED BY BORDER AGENTS NEAR RIO GRANDE, SHERIFF SAYS

Customs and Border Protection said in a news release Tuesday that Border Patrol agents, along with Search, Trauma and Rescue and also Air and Marine Operations, were searching for the girl.

Law enforcement officers from Ciudad Acuna, Mexico, were assisting in the search for the toddler, too.

“Any time a child is lost it is a tragic event,” Del Rio Sector Chief Patrol Agent Raul L. Ortiz said in a statement. “I can not imagine the anguish the parents of this young girl must be feeling and I hope our search efforts pay off with a positive outcome.”

The toddler's disappearance comes just days after a harrowing image of an El Salvadoran migrant and his 2-year-old daughter were pictured lying face down in the Rio Grande. The bodies of Óscar Alberto Martínez Ramírez and his daughter, Valeria, washed ashore about a half-mile from the international bridge that connects Matamoros, Mexico, and Brownsville, Texas.

The image of the two, which highlights the risk that people face while trying to illegally enter the U.S., sparked international outrage.

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A report from the journalist who took the photo alleges the 25-year-old father was frustrated his family was unable to present themselves to U.S. authorities and request asylum — and so he decided to swim across the river on Sunday with his daughter.

Higher-than-average snowfall in the Rocky Mountains is sending more water into the Rio Grande and adjacent canals, creating deceptively swift waters. Border agents have said they are rescuing immigrants from the river on an almost daily basis.

Fox News' Greg Norman and The Associated Press contributed to this report.