If the people supposedly WATCHING the border didn't know these people were tunneling their way into the USA, it's because they weren't paying attention or just didn't care. (After all, there have been multiple people arrested all over the USA who we have no record of, but they are staying at these freebie hotels, eating freebie food and washing their clothes for free and sending their kids to OUR schools and much more).

https://ifapray.org/blog/police-find-tunnel-used-to-smuggle-migrants-over-the-border/