U.S. Customs and Border Protection officers in riot gear on Monday morning blocked the Paso Del Norte international bridge in Downtown El Paso training for the possible arrival of the Central American migrant caravan.

The show of force was part of "operational readiness for the potential impact of the caravan," said Roger Maier, a spokesman for CBP.

The caravan of Central Americans is in southern Mexico more than 1,000 miles from McAllen, Texas, the closest U.S. border crossing.

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Video taken by bystanders and Juárez news media showed vehicle and pedestrian traffic stopped at the borderline at top of the bridge.

Plastic orange barriers were set up to block vehicle traffic. Masked CBP officers with rifles stood guard and other officers in helmets arrived with riot shields as a helicopter hovered above.

"We aren’t going to allow a large group to enter the U.S. unlawfully," said Maier, adding that similar preparations are taking part all along the border.

Preparations began last week and will continue as CBP monitors the situation regarding the migrant caravan, Maier said.

CBP does not have a date or a location where the caravan may arrive on the U.S.-Mexico border "but we do have to be prepared," Maier said.

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While vehicle and pedestrian traffic was halted at the borderline, CBP officers at inspection stations at the foot of the bridge continued processing border-crossers already on the U.S. side, Maier said.

In a statement, CBP said it was assessing the capabilities of its facilities throughout the Mexican border, including operational readiness exercises and the mobilization of resources to ensure lawful trade and travel.

On Sunday, the caravan had reached San Pedro Tapanatepec in the state of Oaxaca in southern Mexico.

The Arizona Republic reported that several migrants said that the caravan, which is moving at about 25 miles a day, was headed to Tijuana, a journey of more than 2,000 miles that on foot could take at least 90 days.

Migrants sleeping on bridge

There have been groups of other migrants sleeping on the Mexican side of the Paso Del Norte Bridge waiting to be allowed into the United States to seek political asylum.

Juárez city officials reported there 20 migrants from Russia, Cuba and Central America staying at the bridge as of Saturday when firefighters went to check on their welfare because of the cool early morning temperatures.

The number of migrants sleeping on the bridge had grown to 70 as of Sunday, NetNoticias.MX reported. The Mexican Red Cross was providing assistance.

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Juárez civil protection authorities were continuing to monitor the situation.

A similar situation occurred last summer with Central American migrants waiting on the Mexican side after stopped by CBP officers at the top of the bridge.

CBP officials have said that migrants were stopped by CBP officers posted at the top of the bridge because CBP didn't have the space to process them.

Immigrant rights advocates claim the tactic is intended to dissuade immigrants from seeking political asylum.

Daniel Borunda may be reached at 546-6102; dborunda@elpasotimes.com; @BorundaDaniel on Twitter.