Prediction markets are under new scrutiny from Congress as lawmakers mull a ban on members betting on the platforms.

The House Oversight and Government Reform Committee officially launched an investigation Friday into insider trading on the platforms, spurred by suspicious bets on the capture of Venezuelan President Nicolás Maduro and the war in Iran.

Committee Chairman James R. Comer, R-Ky., sent letters to Kalshi and Polymarket requesting information on how the companies verify users’ identities, their geographic restriction policies, procedures related to suspicious trades and records of specific trades related to Venezuela and the war in Iran. The letters come after Comer indicated in an interview on Fox Business last week that the committee would begin an investigation.

In an interview with CNBC on Friday, Comer signaled his support for banning people within Congress and the government from trading on prediction markets. He’d previously seemed open to the idea but unsure of current law.

“We want to not only launch the investigation to see how widespread this has been thus far, but also to prove a case that we’ve got to pass some type of legislation,” Comer said. “And I think it wouldn’t be too much to ask, to say members of Congress can’t participate in the predictions market, nor can government employees or people in the president’s administration.”