Mexican security forces clashed with determined Central American migrants as they waded across a river in Guatemala into Mexico on Monday to continue their journey to the United States.

Tear gas was fired on the migrants, some of whom threw rocks at Mexico's national guard militarized police, Reuters reported. The scramble of the mostly Honduran caravan led to some parents being separated from their children as they tried to avoid Mexican immigration agents.

Monday's incident at the Suchiate River, which separates Mexico and Guatemala, underscores the challenges facing Mexican authorities tasked with containing the large group of migrants at the behest of the Trump administration.

The latest group set off from San Pedro Sula, Honduras, last week in hopes of reaching the U.S. southern border to apply for asylum.

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Reuters reported Mexican authorities standing on the banks of the river intent on thwarting the illegal crossing, while hundreds of others ran into Mexico.

“You have two options: You go back to Guatemalan territory or you come with us,” Mexican immigration agents said to migrants who had crossed the river.

“We didn’t come to stay here. We just want to cross to the other side,” said Ingrid, 18, a Honduran migrant. “I don’t want to go back to my country because there is nothing there, just hunger.”

Those caught will be taken to immigration stations and be returned to their home countries if their legal status cannot be resolved. Over the weekend, 2,000 migrants camped out in Guatemala in the town of Tecun Uman, opposite Ciudad Hidalgo on the Mexican side of the border.

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At least 4,000 people entered Guatemala from Honduras since Wednesday, according to Guatemalan authorities. The latest caravan comes as the Trump administration has enlisted Central American leaders in taking a more active role in stemming the flow of migrants at the U.S.-Mexico border.

Most are fleeing endemic poverty and increasing rates of gang violence.

Denis Contreras, a Honduran who was denied asylum and deported from San Diego, vowed not to give up.

“Here we are, and we're not going anywhere, and if you throw us out, we'll return!” he said.

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More than 1,000 migrants chose to give Mexico a try Monday and were taken to a bus to an immigration center for processing. Authorities there said they blocked more than 2,5000 migrants from entering the country on Saturday as they made their way across a bridge over the Suchiate River.

Daisy Perez,42, who was traveling with her two young children, called a relative during a break in the chaos near the river.

“We’re in Mexico, send us money," she said.

The Associated Press contributed to this report.