A three-year-old migrant boy was found in tears as he wandered alone in a Texas cornfield near the US-Mexico border, officials say.
US Border Patrol agents discovered the boy in the Rio Grande Valley near Brownsville, Texas on Tuesday morning.
His name and phone number were written on his shoes, according to officials.
"We believe the boy was with a larger group that ran when they encountered agents," the US Customs and Border Protection (CBP) tweeted.
He was taken to Fort Brown border station, where he was supervised by agents while efforts were made to find his family, officials say.
Border agents say they were unable to locate his relatives and he "does not speak well enough" to tell them who they are.
He has been taken to a processing facility in Texas, where he remains under the care of child workers.
In a statement, CBP told the BBC the boy was "abandoned by smugglers" who "entered the United States illegally".
Startled by border agents attempting to intercept them, the group fled, leaving the boy on his own in an overgrown field, the agency says.
"Agents requested the assistance of a Border Patrol K-9 team in an attempt to search the field and, in the process, they located a child who was alone and crying," the statement says.
He underwent a medical examination at a local hospital and was found to be in a "good condition" with no injuries.
Until his family makes contact, the US Department of Health and Human Services will take custody of him, CBP says.
The discovery of the boy comes as US Border Patrol agents attempt to grapple with the rising number of families trying to reach the US from Central America.
On Monday, Mexico detained nearly 400 Central American migrants who were travelling towards the US border, according to officials.
The migrants, said to be part of a 3,000-strong caravan, were arrested during a raid in Chiapas state.
US President Donald Trump said the remainder "must be apprehended" and threatened to close a section of the border if they were not.
What are the latest migration figures?
In total, 207,475 people have been apprehended on the south-west US border between January and the end of March this year, official US Border Patrol figures show.
Of that total, 53,077 of them were families and 8,975 were unaccompanied children in March, the agency says.
The total number of apprehensions rose sharply between February and March, from 66,884 to 92,607, according to the latest figures.
In March, CBP said encounters of family units and unaccompanied children along the southwest border rose to numbers not seen since 2014.
"We are currently experiencing a system-wide emergency in our processing and holding facilities," CBP deputy commissioner, Robert Perez, said in a statement.
"The humanitarian crisis created by a massive influx of family groups and unaccompanied children in recent months has forced CBP to reallocate resources away from law enforcement, trade and travel missions to process and provide care for those in our custody."
How is Trump dealing with it?
Mr Trump has taken a hard line on migration across the US-Mexico border since taking office in 2017.
Building a "big, beautiful" wall to stop the flow of migrants was one of his main 2016 presidential campaign pledges, blaming Mexico for "bringing drugs, bringing crime, their rapists".
His plans reached an impasse last year after Congress refused to give Mr Trump the $5.7bn (£4.5bn) he wanted to build the wall, leading to a government shutdown.
But in February, Mr Trump managed to circumvent Congress by declaring a national emergency, allowing him to reroute funds from the military to the wall.
As president, Mr Trump has repeatedly threatened to shut down the border if Mexico does not do more to stop undocumented migrants making the crossing.