SAN DIEGO – Troops from Camp Pendleton reported for their first day of work Thursday along the U.S.-Mexico border, part of President Donald Trump’s show-of-force response to thousands of Central American migrants traveling in caravans toward the southwestern border.

The Marines will start by placing barriers along the border, said Michael Kucharek, a spokesman at U.S. Northern Command.

Details on where the barriers will be placed or what kind of materials will be used were not available Thursday.

Several Marines and large military trucks could be seen staging near the San Ysidro Port of Entry Thursday morning, the San Diego Union-Tribune reported.

Officials with U.S. Customs and Border Protection and the U.S. Department of Defenseplan to hold a joint news conference on “Operation Secure Line” on Friday to provide more information.

So far, some 1,300 troops have been assigned to support operations along the California-Mexico border. About 1,100 are already serving at Camp Pendleton with the 1st Marine Expeditionary Force as part of a special purpose marine-air-ground task force, officials said Thursday.

They will be deployed in waves as needed, Kucharek said.

Another 1,500 troops have been deployed in Arizona and 2,800 in Texas as of Thursday, the DOD said. The total number is expected to grow to more than 7,000 active duty troops supporting the mission.

Read more at San Diego Union-Tribune.