U.S Customs and Border Protection conducted a "large-scale operational readiness exercise" Thursday at San Ysidro Port of Entry, which the agency warned could result in processing delays at the busy border crossing.
The CBP announced its plans for the drill Wednesday. By 1 p.m. Thursday, the operation was underway, with many CBP officers and agents taking part. It was scheduled to last around 10 minutes.
Before the drill began, CBP personnel could be seen suiting up in riot gear. Some carried shields. Once the operation began, CBP officers and agents marched toward the U.S.-Mexico border.
Soon, smoke and flash bangs were heard.
The CBP had advised that the drill would be highly visible to travelers crossing the border at that time.
NBC 7's Artie Ojeda was at the border crossing and captured the drill, minute-by-minute. At 1:05 p.m., traffic coming into the U.S. from Mexico at the port of entry was stopped due to the drill.
By 1:18 p.m., vehicle traffic coming into the U.S. at the port of entry had resumed.
San Ysidro is the border’s busiest crossing, with about 110,000 people using it to enter the U.S. every day. That traffic includes some 40,000 vehicles, 34,000 pedestrians and 150 to 200 buses.
During the drills, CBP officers and Border Patrol agents, some dressed in riot gear, formed a line across the ports' traffic lanes and temporarily stopped traffic.
Dave Patterson with Veterans for Peace said his biggest concern was the possible participation of active duty military.
An NBC 7 camera crew spotted people in fatigues participating in the drill but we couldn't confirm if they were active duty military or reserves, or maybe members of the national guard.
That information typically comes from CBP spokespeople but they've all been furloughed during the government shutdown.
Loud bangs were heard and smoke was seen during the drill at the Otay Mesa Port of Entry on Dec. 1.