The House Oversight Committee said on Friday that it is opening an investigation into Kalshi and Polymaket over alleged incidents of insider trading by users of the prediction markets. 

Rep. James Comer of Kentucky, the panel's chairman, sent letters to Kalshi CEO Tarek Mansour and Polymarket CEO Shayne Coplan requesting internal documents to determine what the companies are doing to deter insider trading.

Specifically, Comer asked Kalshi and Polymarket to provide information on how they investigate potential insider trading and on the identity verification processes for domestic and international account holders.

Polymarket and Kalshi allow users to speculate on the outcome of future events, such as elections, sports and geopolitical developments. While their popularity has skyrocketed, they've also drawn scrutiny from lawmakers after a series of suspiciously timed bets sparked concerns about insider trading.

In his letter on Friday, Comer requested information from Mansour and Coplan on trading activity on their platforms tied to the Iran war and to the Trump administration's capture of former Venezuelan leader Nicolás Maduro.  

According to a recent "60 Minutes" report, an investigation by data analytics firm Bubblemaps found that 9 Polymarket accounts made a total of $2.4 million by correctly guessing the dates of pivotal moments in the conflict.

In April, federal prosecutors charged a U.S. special forces soldier with allegedly using confidential government information to bet on Maduro's removal from office, a trade that netted more than $400,000. 

The soldier, Gannon Ken Van Dyke, 38, has been charged with unlawful use of confidential government information for personal gain, theft of nonpublic government information, commodities fraud, wire fraud and making an unlawful monetary transaction. He has pleaded not guilty.

In a statement to CBS News on Friday, a Polymarket spokesperson said the company "maintains a comprehensive market integrity framework."

Kalshi also touted its efforts to prevent insider trading. Spokesperson Elisabeth Diana told CBS News that the company has implemented "comprehensive" safeguards.

In recent months, both platforms have tightened their rules to prevent users from trading on confidential information.

In April, Kalshi fined three congressional candidates and suspended their accounts on the platform for five years after a company investigation found they gambled on their own elections. The prediction market platform now bans members of Congress from creating accounts.

A new rule Polymarket implemented in March also prohibits traders from betting on an event if they "hold a position of authority" or influence that could affect its outcome.