Amid pressure from Washington, Mexico is backpedaling on promises of better treatment for Central American migrants, leaving hundreds stranded in unsanitary camps near its southern border amid allegations of irregular detentions.

Mexican President Andres Manuel Lopez Obrador promised more humane treatment for Central American migrants when he took office in December. His left-leaning government issued thousands of year-long humanitarian visas in January, giving migrants legal access to jobs and the right to travel to the United States.

However, caught off guard by a surge in arrivals, Lopez Obrador's administration is resorting to old tactics based on tough law enforcement.