U.S. Customs and Border Protection officers inspecting vehicles crossing the Mexican border into California discovered two illegal immigrant women hidden in a secret compartment of a car. 

CBP officers made the discovery on Wednesday at the San Ysidro port of entry, located just south of San Diego. San Ysidro is one of the busiest crossings in the U.S. 

Around 5:30 p.m., a CBP officer conducting inspections for entry into the U.S. noticed a "nervous" looking 66-year-old man driving a gray 2008 Hyundai Santa Fe, CBP said. The officer took the man aside for further inspection of the vehicle. 

A human and drug detector dog alerted officers to the underside of the Hyundai’s trunk. Officers checked the area and discovered a built-in compartment in the rear trunk area and found two women hiding inside. 

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The officers had to remove the screws and covers for the compartment to help the two individuals get out. CBP said the women were both Mexican citizens, ages 25 and 37, with no legal documentation to enter the U.S.

"It’s incredibly dangerous for people to be placed inside a vehicle compartment they can’t get themselves out of," said Sidney Aki, Director of Field Operations for CBP in San Diego. "These two women were lucky that their attempt to try and enter the U.S. illegally this way didn’t end in serious injury or worse."

CBP said the women will be deported to Mexico and the driver will face smuggling charges. No further information was released. 

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Data from CBP suggests that illegal border crossings have risen in the past year. Many of their encounters are immigrants from El Salvador, Guatemala, and Honduras.