Short-seller Hindenburg Research, which in recent months has taken aim at firms including Nikola Corp and DraftKings Inc, announced a reward of up to $1 million for information on the reserves that back cryptocurrency Tether.
In a statement on Tuesday, the short-seller said Tether's disclosures around its holdings have been "opaque".
The U.S. Commodity Futures Trading Commission fined the company behind Tether $41 million last week to settle civil charges over allegedly making misleading statements and making illegal transactions.
Tether is a major player in the stablecoin market. Stablecoins are digital tokens usually backed by reserves of dollars or assets.
The company behind Tether did not immediately respond to a Reuters request for comment.
(Reporting by Niket Nishant in Bengaluru; Editing by Shounak Dasgupta) ((Niket.Nishant@thomsonreuters.com))