Broken Bonds: CNBC investigates how so many lost so much in Puerto Rico

A six-month CNBC investigation found that top executives at UBS Americas headquarters had direct knowledge that brokers in Puerto Rico were selling funds packed with risky Puerto Rican bonds, even as the economy was crumbling. Thousands of residents put their life savings into these funds and lost nearly everything when the bond prices plummeted. CNBC obtained about 2,000 pages of internal emails, arbitration filings and other confidential documents that show top executives at the company knew what was going on with the risky bond funds, but did little to stop it. The investigation airs on Monday on cnbc.com and CNBC.