Mexico on Tuesday sought to block a caravan of around 100 Central American migrants seeking to reach the United States.
It was the second attempted caravan crossing in three days, with a far larger caravan of about 1,000 US-bound migrants entering Mexico on Sunday.
Local news footage showed Mexico's National Guard, immigration authorities and police in Chiapas state positioned across a road to stop the migrants after they crossed the Suchiate River on the southern border with Guatemala.
As officers surrounded them, the migrants began running. Around 40 were detained, according to reports from Tapachula, the city closest to the border.
Mexican immigration authorities did not immediately respond to AFP requests to confirm the arrests.
The previous caravan of around 1,000 migrants crossed the border on Sunday evening without encountering resistance.
They stopped in Tapachula before resuming their journey toward the United States, although the border remains virtually closed.
"Our destination is the United States," said Cesar Sandoval, a 47-year-old Nicaraguan who arrived Sunday.
After the electoral victory of Democrats during the midterm elections last week, he hopes to have "another chance" to enter the United States.
President Donald Trump's party took a thrashing as voters responded to rising prices and the unpopular Iran war, with Republicans losing seats to Democrats in stronghold states like Texas, Kansas and the Carolinas.
"We hope they remember that the ones who gave them the vote so they could make it to the Senate and Congress were the sons of Hispanics, the sons of Latinos," Sandoval added before continuing his journey.
The group, including many families toting babies and dogs, walked on a highway near the Pacific coast with their belongings. Some were carrying flags from Honduras, El Salvador and Guatemala.
This is the third caravan to seek a future in the United States since September.
The other two groups were broken up before leaving the border state of Chiapas, and granted temporary stay permits by immigration authorities.
Trump derided caravans of undocumented migrants during his first term, and under the subsequent presidency of Democrat Joe Biden.
"God is coming with us on this journey. The United States offers better opportunities than Guatemala," said 38-year-old Cristian Pablo, carrying his national flag on the long walk north.
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