Las Vegas Underground Question

Can any Las Vegas native / insider offer some insight into the following ? I saw a show awhile back and I can't remember if it was National Geographic or Las Vegas CSI or both. It talked about the Las Vegas underground, an area where there are city sewers that have been taken over by squatters, transients etc.

I'm sure all cities have this problem, but the show I had watched indicated it was very pronounced such that it was compared to almost an underground city. Rows of cardboard box homes filled with homeless people stretching well into the tunnels. I can't remember whether this was fact or fiction.

Does anyone have a better idea?

A simple google search would tell you that it is, indeed, fact.

http://abcnews.go.com/Nightline/las-vegas-strip-home-homeless/story?id=8652139

yeah, it's fact. And it's pretty dangerous for those folk when it rains. yes it does occasionally rain and it doesn't take much rain for those tunnels to become pretty dangerous.

Here's a book about it for $15. Also available as an e-book for $8.

http://www.shoplva.com/products/beneath-the-neon

Oh, quite true.
Remember the land under the old Imperial Palace was considered worthless because it was a flood channel until one brave entrepreneur built the Imperial Palace there and did very well for himself. Now its the Linq or something but its still a flood channel.