WATCH Migrants From Caravan Climbing Fence on US Southern Border

Asylum-seekers from the first wave of the politically-charged Central American migrant caravan began climbing the US border fences on Wednesday, after arriving at the northern Mexican city of Tijuana.

A group of hundreds of migrants reached Tijuana, located directly across the US-Mexico  border from California's San Diego County, the New York Times reported. There are approximately 800 people in the group, local officials and advocates told the newspaper; however, another 4,000 migrants are expected to reach the border in a matter of days.

READ MORE: First Group of Central American Caravan Migrants Arrives at US Border — Reports

At least nine migrants from the caravan have already tried to cross the border and get to the US side, where they were promptly arrested by border patrol officers. Following US President Trump’s executive order, issued last week, migrants who do not cross at official border posts will no longer be allowed to request asylum, and face automatic deportation.

Many of the migrants in Tijuana say they will wait for the rest of the caravan to arrive before trying to cross, AFP reports. Authorities in Tijuana said they expected between 1,500 and 2,000 migrants associated with the caravan to arrive by the end of the day on Thursday, noting that such an influx could possibly overwhelm the city’s resources.

Earlier on Wednesday, US Defense Secretary Jim Mattis travelled to Texas to meet with some of the 5,600 American troops who'd been deployed to support border security. Mattis said military deployment was "necessary" to support the US Border Patrol in a number of ways, from ferrying them around by helicopter to helping create wire fencing along the border.

Another 2,000 migrants have arrived at the town of Navojoa, which is 1,200 kilometres (750 miles) from Tijuana, where they plan to cross the border. According to AFP, because of the transport provided by Mexican authorities, who felt it would be easier to give the migrants the means of transportation than a shelter, the whole 5,000 migrant-caravan could arrive at the US border by Friday.

Several caravans of migrants, mostly from Central America's "Northern Triangle" — El Salvador, Guatemala and Honduras — have started to make their way across the territory of Mexico to reach the border with the United States. The US government has reported plans to deploy 15,000 troops to its border with Mexico to address the issue of the approaching caravan of migrants seeking asylum in the country, while Trump had warned that the caravan included “hardened criminals” and “unknown Middle Easterners” who intended to “assault” the United States.