That means owners of casinos in Australia's five most populous cities now face enforcement investigations that could carry fines or restrict their licences. "We have an enforcement investigation under way at Crown casino that demonstrates the seriousness of our concerns. And we also have significant compliance work under way on the casino sector," Rose wrote. The crackdown may meanwhile complicate a A$9 billion buyout by Star of larger rival Crown, which has been fielding takeover approaches. Crown shares were down 1.5% in a flat overall market and Star shares were down 3%.