Mexico has detained nearly 400 Central American migrants who were traveling through the south of the country trying to reach the US border, officials say.
Monday’s operation in Chiapas state targeted a group of some 3,000 migrants which included small children.
It is said to be the largest single raid on people traveling in so-called caravans. Officials say those detained had refused to apply for visas.
Mexico is under pressure from the US to stem the flow of people heading north.
There has been a huge increase in men, women, and children fleeing El Salvador, Honduras and Guatemala, the three countries where most of those seeking asylum on the US-Mexico border come from.
President Donald Trump again threatened to close the border if Mexico did not do more to stop the undocumented migrants.