Saipan casino operator Imperial Pacific’s runaway success in attracting VIP gamblers may have also attracted the interest of US financial watchdogs.

On Sunday, Bloomberg ran a feature report on the success of Imperial Pacific International Holdings’ temporary casino Best Sunshine Live. The property has posted some truly impressive VIP gambling figures in recent months, including back-to-back months of nearly $4b in VIP turnover.

However, Saipan is part of the Northern Mariana Islands (CNMI), a commonwealth of the United States, and Bloomberg’s sources claim that the US Treasury Department’s Financial Crimes Enforcement Network (FinCEN) has “taken notice of the activity” at Best Sunshine.

Best Sunshine currently boasts only 16 VIP tables, but each of these tables generated daily revenue of $170k over the first half of 2016, dwarfing the returns of tables in some of Macau’s major integrated resorts. Further highlighting this discrepancy, Bloomberg quoted a local activist describing Best Sunshine as “a duty-free store with a fresh coat of paint and some chandeliers.”