Thousands of Hondurans, including many families with children, walked together across Guatemala on Saturday hoping to reach the US.
They are fleeing poverty and violence in a region battered by the Covid-19 pandemic and back-to-back hurricanes late last year.
Between 7,000 and 8,000 migrants have entered Guatemala since Friday, according to the country's immigration authority, and are heading towards the Mexican border, where Mexican authorities sent troops and riot police.
Once the caravan reaches Mexico, it is likely to be subjected to pressure to break up. Mexico's migration agreement with the US is still in place, meaning the caravan would be dispersed, a Mexican official said.
The first migrant caravan of the year comes less than a week before US president-elect Joe Biden takes office, promising a more humane approach to migration, in contrast to outgoing President Donald Trump's hardline policies.
In the meantime, Mexican and Central American authorities co-ordinated security and public health measures aimed at deterring mass unauthorised migration across the region.
Guatemala, Honduras and Mexico sent thousands of security forces and the Guatemalan military detained hundreds of migrants on Friday.
The caravan has nevertheless grown considerably over the past 24 hours, with members citing a worsening crisis of hunger and homelessness in Honduras as their reasons for joining.
"We have nothing to feed to our children, and thousands of us were left sleeping on the streets," said Maria Jesus Paz, a mother of four who said she lost her home in the hurricanes.
"This is why we make this decision, even though we know that the journey could cost us our lives."
Coronavirus-related lockdowns shattered Honduras' economy, which last year suffered its worst contraction on record.
"First I lost my job because of the pandemic and then I lost my home in the hurricanes," said Melvin Paredes, who joined the caravan with his brother.
"The only thing I have left is to fight for my family's survival."
