Nov. 19 (UPI) -- Customs officials temporarily shut down the northbound San Ysidro, Calif., border crossing Monday morning to increase security at the port of entry.
U.S. Customs and Border Protection announced the closure around 3 a.m. The closure also affected northbound pedestrian traffic.
"CBP has temporarily suspended northbound vehicle processing at San Ysidro to position additional port hardening materials," the agency said in a tweet. "After the materials are in position, CBP will resume processing northbound vehicle traffic in select lanes. Southbound vehicle lanes remain unaffected."
CPB reopened some lanes of traffic about three hours later after installing jersey barriers and concertina wire.
The move came as a group of Central American migrants makes its way north through Mexico, some to seek asylum in the United States.
CPB said it received reports that the migrants, whom the administration has repeatedly referred to as a "caravan," were planning to gather in Tijuana, Mexico, "for a possible attempt or attempts to rush illegally through the port of entry instead of presenting themselves as required to a CBP officer."
Officials said no large groups attempted to force their way through the U.S. border.
"CBP will not allow for the unlawful entry of persons into the United States, at or between our ports of entry," said Pete Flores, director of field operations in San Diego. "Waiting until a large group of persons mass at the border to attempt an illegal crossing is too late for us; we need to be prepared prior to when they arrive at the border crossing."
The closure came as the United States works to increase security along the southern U.S. border with Mexico. The Department of Defense deployed 5,900 troops to the border to assist border patrol officials.
The duties of the troops sent to the border will be limited in scope. They will assist Border Patrol agents along with the 2,100 National Guardsmen sent earlier this year.
They will not, however, confront any migrants who attempt to enter the United States.
The troops can transport border agents to locations as needed, build temporary structures, set up wire barriers, and provide medical services for military personnel and migrants. Troops cannot make arrests, seize drugs or conduct searches of migrants.