BASSETERRE, St. Kitts (AP) — The U.S. Treasury has alerted financial institutions that some people are abusing a citizenship-by-investment program in St. Kitts & Nevis, which has become increasingly reliant on revenue from selling citizenship to foreigners.

The tiny Caribbean nation, less than twice the size of Washington D.C., offers foreigners a very fast path to citizenship in exchange for a minimum real estate investment of $400,000 or a $250,000 donation. It has long insisted its background checks are thorough and the program is well managed, although there has been little public accounting.