Myth of 90 percent: Only small fraction of guns in Mexico come from U.S.

You've heard this shocking "fact" before -- on TV and radio, in newspapers, on the Internet and from the highest politicians in the land: 90 percent of the weapons used to commit crimes in Mexico come from the United States.

But, it's not even close, according to a Fox News investigation. The fact is, only 17 percent of guns found at Mexican crime scenes have been traced to the U.S.