Border Patrol agents discovered 30 migrants, including an unaccompanied minor, in the back of a semitrailer Saturday night at an Arizona checkpoint around 25 miles north of the U.S.-Mexico border.

Tuscon agents referred the truck for a secondary inspection after a Border Patrol dog alerted to the vehicle. During the inspection, agents found 29 illegals from Mexico and one from Ecuador hidden in the back of the truck.

The 30 foreign nationals were arrested and will be processed for immigration violations. The driver and a passenger were arrested and will face human smuggling violations.

A Border Patrol agent, Joe Curran, stressed the danger these kinds of situations pose. “They’re all locked in the back with no way out, surrounded by other cargo being shipped,” he told Fox News. “It’s a super-hazardous situation for everyone involved.” He said the Border Patrol has seen these kinds of situations for a long time, but they’ve ramped up their efforts to detect them due to their potentially life-threatening nature.

Last week, in a case with eerie echoes of this one, 39 bodies were discovered in the back of a truck in England. The episode is thought to have been a case of human trafficking; the bodies were those of Chinese nationals, likely looking to migrate to England.

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In 2017, 10 migrants attempting to enter the U.S. baked to death in a sweltering trailer in Texas. The truck’s refrigeration system did not work and the ventilation holes were clogged.

Curran said they’ve seen an “acute uptick” in human smuggling operations of late. “This is the second instance of 30 people in the last two weeks.”

On Oct. 16, 32 migrants were found hiding in the back of a semitrailer, according to AZ Central. The migrants were found via X-ray detection. The area where the migrants were hiding was 47 degrees at the time they were found, officials said.

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In response, the Department of Homeland Security has launched “Operation Safeguard” to make both the general public and the trucking industry aware of the life-threatening dangers of human smuggling using commercial trucks.

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On Tuesday, border officials sounded the alarm over a surge in hard drugs, weapons and gang members caught coming into the U.S. from Mexico. In Fiscal Year 2019, 16,000 criminal illegal aliens were caught.