It’s not just Teslas zooming through Elon Musk’s tunnels under the Las Vegas Convention Center, chauffeuring passengers as part of a public transit experiment that started in 2021.

A skateboarder got into a tunnel through one of the established passenger pickup stations, forcing staff to briefly tell drivers to stand by while they ejected the interloper.

Someone else got in through another station when the transit system wasn’t running, and started taking photos underground until security arrived.

Then there are the unauthorized cars that have repeatedly tailgated the Teslas into the tunnel stations, sometimes getting in before the automated security gates have a chance to close behind.

Trespassing in the tunnel system has become a headache for the Boring Company, which built and operates the 2.4-mile subterranean road network known as the Loop. People break the rules by going where they’re not supposed to, forcing the company or convention center to intervene and escort them out.

There have been at least 67 trespassing episodes since 2022. And since the beginning of last year, 22 vehicles have followed the Teslas into the stations or tunnels, according to reports from the Boring Company that Fortune obtained via a Freedom of Information Act request with the Las Vegas Convention and Visitors Authority.

In the monthly reports it submits to the agency, Boring discloses problems like property damage, theft, technical issues, or injuries, near-misses, and trespassing or intrusions. For the trespassing, it provides a brief description of what happened, such as vehicles tailing a Tesla to get in and then a staff technician escorting the unauthorized vehicles out. The disclosures don’t say whether trespassers tried to evade being caught, or any reasons they gave for being on the property. Some of the incidents appear to be accidental, and many of them took place in the aboveground stations or buildings, and not necessarily inside the tunnels themselves.

Of the cars that slipped onto the property, all of them did so “inadvertently,” according to a convention and visitors authority spokesperson. Their drivers followed the Boring Company’s vehicles “believing they were accessing a ride-share pickup spot or entry to parking, and were immediately directed out.” Only one such incident “resulted in a tunnel intrusion,” the spokesperson said.

To avoid problems, the authority and the Boring Company have installed a license plate reading system that automatically closes the tunnel gate when it doesn’t recognize car license plates entering at a surface station. The authority also said it is “actively working with [the Boring Company] to eliminate opportunity for inadvertent intrusion.”

None of the records provided disclosed whether the Boring Company ever called the Las Vegas Metropolitan Police about trespassing. Contacted by Fortune, a police spokesman said they didn’t know of any incidents for which the agency dispatched officers.

Boring Company did not respond to a request for comment for this article.

The tunnel system is a far cry from the lofty, high-speed, and autonomous hyperloop system Musk initially hoped to build with his tunnel-digging venture. Musk had envisioned sci-fi systems for cities worldwide that would shoot pods carrying passengers through underground tubes at hundreds of miles per hour.

But while Boring continues to develop a new kind of tunnel boring machine, it has yet to develop a hyperloop or new transit technology. Instead, Boring has built its only operational transit system in Las Vegas that uses low-tech human-driven Teslas to ferry passengers underground, free of any traffic jams on surface roads. Boring has had conversations with officials about tunnel projects in many other cities, including Baltimore and Chicago, but those all went nowhere, and Boring has now focused its full attention on the Las Vegas project.

Behind the scenes, former employees who dug the initial tunnels in Las Vegas have raised serious concerns about their safety while doing so, and there have been dozens of injuries as the company moves quickly to expand its system, as Fortune reported earlier this year. In one snafu, Boring workers dug too close to a pillar for the Las Vegas monorail, and the convention center authority had to briefly shut the monorail down while determining whether the pillar had become unstable.

Boring currently employs some 204 drivers to shuttle passengers in various Tesla models below the convention center, according to records from June. Between opening day in June 2021 and November 2023, more than 2 million passengers used the system, according to the convention and visitors authority, and the agency reports high customer satisfaction scores.

Based on the reporting, regular passengers have caused relatively few problems. Those include occasional unruliness or someone bumping their head on a Tesla trunk while reaching for their baggage.

Currently, the tunnel transit system is open only to conference attendees, and not the general public. Boring has started opening and operating stations just outside the convention center’s jurisdiction, but those routes are still linked to the existing tunnel system and are paid rather than free. The company is working to get approvals from the City of Las Vegas to start building 68 miles of tunnels underneath the city and in other areas of the county, including to the airport.

The system Boring has built in Las Vegas—small tunnels with funky pink, blue, and green lighting—has nevertheless captured the public’s attention. That includes people who aren’t supposed to be in them.

In one case, two people were found sleeping in one of the tunnel stations located near one of the convention center parking lots. They were ultimately escorted off the property by Boring’s security. In another incident, a man tried to remove a license plate reader at one of Boring’s stations, and convention center security also escorted him off the property.

Remember, when riding the Loop, be sure to follow the rules. Riders have their conference attendee credentials with them. And no skateboarding or wandering the tunnels alone.

Do you have an insight to share? Got a tip? Contact Jessica Mathews at jessica.mathews@fortune.com or through the secure messaging app Signal at 479-715-9553.

More coverage from Fortune on the Boring Co.:
– ‘We have consistently flirted with death’: Elon Musk wanted the Boring Co. to build a tunnel system below Las Vegas. Former employees say they feared for their lives while working there
– Workers at Elon Musk’s Boring Co. accidentally dug too close to a supporting column of the Las Vegas monorail last year, forcing officials to briefly halt service

This story was originally featured on Fortune.com