A 3-year-old migrant boy found in a field at the Mexico-Texas border Tuesday morning -- with his name and a phone number scrawled on his shoe -- had likely been abandoned in the dark, desolate space by smugglers, U.S. Customs and Border Protection agents said.

The CBP said Tuesday officials were working to contact the toddler’s family.

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NBC News reported the boy was crying and in distress when agents discovered him near Brownsville, which is at the eastern edge of the U.S.-Mexico border in South Texas’ Rio Grande Valley.

CBP said the boy will likely be sent to a facility for unaccompanied minors that is operated by the U.S. Department of Health and Human Services.

Rudy Karish, who is the chief agent in the Rio Grande Valley, said the boy was most likely left in the field by smugglers who took off after spotting border agents. Karish said the boy was “in good spirits.”

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U.S. Customs and Border Protection apprehended nearly 9,000 unaccompanied minors just in March and more than 20,000 since January, as border crossings surged compared to recent levels. The agency said Wednesday that it could not provide a breakdown by age. The number of people in families -- parents and children -- who were reported to have crossed the border last month reached 53,077, NBC News reported.

The Associated Press contributed to this report.