At least 4,500 Honduran migrants headed north to the United States in hopes of a better life crossed into Guatemala Friday night, with border agents putting up no resistance, an AFP correspondent said.
The estimate of the number of people crossing over came from a Guatemalan police official at the border town of El Florido.
He said police let the migrants in because the crowd included many families with children.
Seeking to escape poverty, unemployment, gang and drug violence and the aftermath of two devastating hurricanes, the migrants plan to walk thousands of kilometers through Central America to Mexico and then on to the US.
They are seeking a better life in America under Joe Biden, after years of tough anti-immigrant policy under Donald Trump.
The quest is likely to end in heartbreak for many, with American authorities already having warned off the group. The group set off from Honduras earlier Friday.
Biden has promised "a fair and humane immigration system" and pledged aid to tackle the root causes of poverty and violence that drive Central Americans to the United States.
But Mark Morgan, acting Commissioner of the US Customs and Border Protection, warned the group last week not to "waste your time and money."
The US commitment to the "rule of law and public health" is not affected by the change in administration, he said in a statement.
More than a dozen caravans, some with thousands of migrants, have set off from Honduras since October 2018.
But all have run up against thousands of US border guards and soldiers under Trump, who has characterized immigrants from Mexico as "rapists" who were "bringing drugs" and other criminal activity to the United States.
Mexican authorities said late Thursday that 500 immigration officers were being deployed to its border with Guatemalan in anticipation of the caravan's arrival.