TIJUANA, Mexico (AP) — Mexico looked set to shore up security near its border with the United States on Monday, as police lined up outside a shelter in the city of Tijuana and told Central American migrants they couldn’t walk toward the border area.

Mexico’s National Migration Institute said that 98 migrants were being deported after they tried to breach the U.S. border, and U.S. agents fired tear gas into Mexico to stop them. Mexico’s Interior Department said about 500 migrants were involved in the attempt to rush the border, while U.S. authorities put the number at 1,000.

Mexican officials said the migrants had taken part in “violent” chaos, which originally began as a peaceful march to appeal for the U.S. to speed processing of asylum claims for Central American migrants marooned in Tijuana.

U.S. Customs and Border Protection Commissioner Kevin McAleenan said on a call with reporters that 69 migrants who tried to cross the border illegally were arrested on the California side.

He said the Border Patrol’s use of force policy allows agents to use tear gas and other non-lethal methods, but the incident would be reviewed and the situation was resolved without serious injury.

“As the events unfolded, quick, decisive and effective action prevented an extremely dangerous situation,” he said.

But on Monday, the incident had left many migrants sullen, wondering whether the unrest had spoiled whatever possibilities they might have had for making asylum cases.

Isauro Mejia, 46, of Cortes, Honduras, looked for a cup of coffee early Monday morning after spending the day prior caught up in the clash.

“The way things went yesterday … I think there is no chance,” Mejia said.

In rare criticism of the migrants, Mexico’s National Human Rights Commission said it “reiterates that members of the caravans that cross our country should respect Mexican laws and not engage in actions that affect the communities they pass through.”

“It is important to note that the fact the Mexican government protects their rights,” the commission said, “does not imply a free pass to break the law.”

The Sunday incident began after a large group marched to the U.S. border to make the migrants’ plight more visible to the governments of Mexico and the U.S. Some attempted to get through the fencing and wire separating the two countries, leading U.S. agents to fire the tear gas.

American authorities also shut down the nation’s busiest border crossing at San Ysidro for several hours at the end of the Thanksgiving weekend.

Lurbin Sarmiento, 26, of Copan, Honduras, said she had been with her 4-year-old daughter at a concrete riverbed, which had a trickle of water from the Tijuana River, when U.S. agents fired the gas.

“We ran, but the smoke always reached us and my daughter was choking,” Sarmiento said, visibly shaken.

She said she never would have gotten that close with her daughter if she thought there would be tear gas.

Fumes were carried by the wind toward people who were hundreds of feet away.

As the chaos unfolded, shoppers just yards away on the U.S. side streamed in and out of an outlet mall, which eventually closed.

Department of Homeland Security Secretary Kirstjen Nielsen said in a statement that U.S. authorities will continue to have a “robust” presence along the Southwest border and that they will prosecute anyone who damages federal property or violates U.S. sovereignty.

“DHS will not tolerate this type of lawlessness and will not hesitate to shut down ports of entry for security and public safety reasons,” she said.

More than 5,000 migrants have been camped in and around a sports complex in Tijuana after making their way through Mexico in recent weeks via caravan. Many hope to apply for asylum in the U.S., but agents at the San Ysidro entry point are processing fewer than 100 asylum petitions a day.

Francisco Vega, the governor of Baja California, said almost 9,000 migrants were in the state — mainly in Tijuana, with a lesser number in Mexicali — and called it “an issue of national security.” Vega issued a public appeal to the federal government to take over responsibility for sheltering the migrants and deport those who were breaking the law.

Tijuana Mayor Juan Manuel Gastelum on Friday declared a humanitarian crisis in his border city of 1.6 million, which he says is struggling to accommodate the crush of migrants.

The chaos comes as U.S. and Mexican officials wrangle over the issue of migration and discuss how to deal with asylum-seekers waiting in Mexico. With a backlog of cases that number into the thousands, many migrants appear set to linger along the border for months, if not longer.

On Monday, U.S. President Donald Trump took to Twitter to express his displeasure with the caravans in Mexico and to make another pitch for his promised border wall.

“Mexico should move the flag waving Migrants, many of whom are stone cold criminals, back to their countries,” Trump tweeted. “Do it by plane, do it by bus, do it anyway you want, but they are NOT coming into the U.S.A. We will close the Border permanently if need be. Congress, fund the WALL!”

Trump has repeatedly suggested without evidence that the migrant caravans are full of hardened criminals, but they are mostly poor people with few belongings who are fleeing gang violence. During his presidential campaign, he promised he’d have Mexico pay for a wall.

Alex Castillo, 35, of Tegucigalpa, Honduras, walked away on Monday from the shelter in Tijuana where he had spent the night. He said he was planning to head to the northern Mexico industrial hub of Monterrey to find work, and he had a red bed roll slung over his shoulder.

Castillo said he was leaving “to avoiding getting beaten.”

“If they’re launching tear gas, it’s better to head somewhere else,” he said.

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