DPS officers have conducted "enhanced commercial vehicle safety inspections" since April 6 at seven ports of entry—Brownsville, Los Indios, Pharr, Laredo, Eagle Pass, Del Rio, and El Paso. Texas has 28 land ports of entry with Mexico.

Significant slowdowns were recorded at the Pharr-Reynosa International Bridge, with the wait time increasing up to 4 hours, according to real-time data captured on the Customs and Border Protection website. Laredo and Brownsville bridges experienced the same. Wait time is recorded from when a vehicle passes the Mexican toll gate until it clears U.S. customs.

The DPS inspections are occurring on state roads just beyond the ports of entry, which backs-up the line into Mexico.

By end of day April 9, DPS had inspected 2,390 commercial vehicles, of which 552 were placed out of service "for serious safety violations to include defective brakes, defective tires and defective lighting," according to Lt. Christopher Olivarez, DPS spokesman for south Texas.

"Also 73 commercial vehicle drivers were placed out of service. The total number of violations detected thus far is 8,244."

DPS hasn't said how long it intends to continue with the inspections. Mexico is Texas's top trading partner with $88.5 billion worth of goods flowing both ways across the Texas–Mexico border annually, according to Global Edge.

"It's kind of like a Mexican standoff," said Todd Bensman, national security fellow at the Center for Immigration Studies.