Calls are increasing inside Congress for investigations into the prediction market platform Polymarket after the latest instance where groups of anonymous traders made strategic, well-timed bets on a major geopolitical event hours before it occurred.

On Wednesday, The Associated Press reported that at least 50 brand new accounts on Polymarket placed substantial bets on a U.S.-Iran ceasefire in the hours, even minutes, before Donald Trump announced the ceasefire late Tuesday on social media. These were the sole bets made on Polymarket through these accounts.

In January, an anonymous Polymarket user made a $400,000 profit by betting that Venezuelan leader Nicolas Maduro would be out of office, hours before Maduro was captured. In the hours before the start of the Iran war, another account made roughly $550,000 in a series of trades effectively betting that the U.S. would strike Iran and that Ayatollah Ali Khamenei would be removed from office.