Online sports gambling poses an increasing risk of money laundering, the U.S. Treasury Department said in a warning that comes as a record number of Americans are expected to place bets on the coming Super Bowl.

The rapid growth of the sports betting sector and a lack of uniform regulations contribute to “significant and increasing money-laundering risks,” the Treasury said Wednesday as part of an expansive report on money-laundering concerns.

An estimated 67.8 million Americans are expected to bet on Sunday’s Super Bowl, a 35% increase from last year, according to survey results published Tuesday by the American Gaming Association, a trade group. The AGA estimates that 28.7 million of those bettors will place their wagers on a legal U.S. site.

Americans have become prolific gamblers since the U.S. Supreme Court in 2018 overturned a federal law banning sports betting in most states. Since that ruling, U.S.-based individuals have made more than $220 billion in legal sports bets as of 2023, according to the Treasury. Legal sports bets can take place at in-person facilities but most sports betting is done online.