None of the roughly 40 patrons and employees inside the casino at the time of Thursday night's robbery were hurt.
Authorities have no leads yet, said Puerto Rico police chief Emilio Diaz Colon. Puerto Rico is in the midst of a crime wave marked by a dozen murders a week on average and numerous armed robberies.
Authorities attribute most of the mayhem to turf battles over control of the illegal drug trade in public housing complexes, yet the violence has also spread into upscale neighbourhoods favoured by tourists.