U.S. Customs and Border Protection agents recently shut down an incomplete cross-border tunnel in Arizona, and they’ve posted a video online offering America an look inside.

“Check out this rare view inside an illicit, incomplete cross-border drug tunnel discovered on Wednesday,” CBP posted to Twitter Saturday. “This video was recorded by Tucson Sector Border Patrol agents as they crawled through the tunnel.”

The passage, located under a parking lot in Nogales, Arizona, was discovered during a cooperative bi-national tunnel sweep along the U.S.-Mexico border. The tunnel was several meters below street level, and about 75 yards west of the Port of Nogales, DeConcini Crossing.

A specialized tunnel team escorted by Border Patrol International Liaison Units and Mexican police found various cussing and digging tools inside the passage, which originated in a storm drain and extended about 12 feet into the U.S. and five feet into Mexico, according to a CBP statement.

The video shows is a claustrophobic’s worst nightmare.

The tight confines provided just barely enough room to crawl through, and did not appear to contain any bracing or supports to prevent collapse. Border Patrol and Policia Federal are investigating the tunnel and working to fill it in, but no arrests have been made in the case. They’re also soliciting anonymous tips about other suspicious activity and potential tunnels in the area.

Since 2001, U.S. law enforcement have discovered well over 100 tunnels along the border with Mexico, including several in Nogales.

In one Nogales tunnel, authorities discovered 198 bricks of cone, according to a Time photo gallery.

Some are crude holes like the one discovered last week, while others are sophisticated walkways with electricity, ventilation systems, and running water.

In 2016, U.S. officials retrieved more than a ton of marijuana from a tunnel that ran 400 yards between a restaurant in Mexicali, Mexico and a home built by drug smugglers in Calexico, California, BBC reports.

Last fall, U.S. border patrol found another elaborate tunnel stretching 627 feet, including 336 feet into California, that wasn’t quite complete.

“The border patrol said that a solar panel system had been set up to power lighting and ventilation systems inside the tunnel, which was also equipped with a rail system along its entire length, and two pumps to drain water,” according to The Guardian.

Another discovered around the same time ran from an old KFC in San Luis, Arizona for about 590 feet to a home in Sonora, Mexico. Federal officials discovered that passage after the owner of the abandoned KFC was arrested with methamphetamine, cocaine, fentanyl, white heroin, and brown heroin inside tool boxes he hauled out of the building, KYMA reports.

It’s unknown how many illegal immigrants make their way through the underground passageways, but it’s clear there’s plenty of demand for easy ways in to the U.S.

So far in fiscal year 2019 – from October 2018 through April 2019 – federal officials have arrested to or processed 628,194 illegal immigrants on the southern border, according to CBP data. The figure is expected to eclipse total apprehensions for 2018 – 683,178 – in May.

Federal officials contend the 2019 total could eclipse 1 million illegal immigrants crossing into the U.S. for fiscal year 2019, which is forcing the government to take drastic measures to process the massive influx.

“#BORDERNEWS Hundreds of Border Patrol agents from other sectors around the nation, including those who patrol the Northern Border, have made their way to the (Rio Grande Valley) to help after recording breaking apprehensions continue to happen along the Southern Border,” WGBT reporter Sydney Hernandez posted to Twitter on Monday.

Hernandez noted only 60 percent of agents are actually guarding the border.

The others are “on transporting, hospital watch, and feeding and cleaning duty,” she said.