That's kind of like finding ancient stuff in Greece. You dig a hole, and there's some ancient pots and pans in there. It's gotten to the point where people who want to build houses just carry the ancient findings away in the night, because the antiquities service will otherwise deem your plot an archaeological site.
This type of thing happens in most countries. In the USA they actually have to hire bored archeologists to check things out as part of any contract from the federal government (and a lot of state governments) on anything that might have a hint of Native American relics.
