Alabama, Texas and New Jersey are investigating whether the firm's marquee offering violates local securities laws.
The notice did not appear targeted at any one instance of digital asset impropriety.
The U.S. DOJ is reportedly probing Tether and Bitfinex over whether they artificially boosted bitcoin's price using the USDT stablecoin.
Brazil's antitrust watchdog is investigating major banks for potentially collaborating to prevent crypto brokerages from gaining banking services.
NASAA announced Tuesday that regulators are running more than 200 active crypto-related investigations.