The House Oversight Committee is investigating Kalshi and Polymarket over concerns that customers may be using non-public information for insider trading.
Chairman James Comer requested documents from Polymarket and Kalshi to evaluate how platforms verify identities, enforce geographic restrictions, and monitor suspicious trading.
Prediction markets have surged in popularity over the past 18 months. Critics argue some profitable bets appear too accurate to be coincidental.
In April, a US soldier was charged with using classified information to make over $400,000 trading on Polymarket. The company referred the matter to the Justice Department.
Kalshi suspended and fined three congressional candidates for insider trading on bets related to their own campaigns. The firm stated its commitment to policing unfair trading.
Comer cited these cases and said "this growing pattern indicates that Congressional action may be necessary."
Concerns have increased after suspicious trades ahead of President Trump's policy announcements. Lawmakers have asked regulators to investigate.
