Nevada gaming regulators are investigating reports that casino operator Las Vegas Sands allowed the use of ‘shills’ to conceal the identities of Chinese VIP gamblers.

Last month, Reuters reported that Sands was suing two Nevada housekeepers to collect $6.4m in gambling debts the two Chinese nationals had allegedly run up at Sands’ Venetian and Palazzo casinos in Las Vegas. The women claimed they were merely fronts who signed IOUs for the real VIPs in exchange for a couple thousand dollars apiece.

On Tuesday, Reuters quoted sources saying that the Nevada Gaming Control Board was investigating the allegations made by the two women. Specifically, the GCB is said to be examining whether the use of such shills violates state bookkeeping rules and its gaming licensees’ “decency” requirements.

Sands spokesman Ron Reese confirmed to Reuters that the GCB “has made inquiries related to this matter and we’ve responded in a timely and transparent manner, as we always do.”