The White House has told aides not to place bets on prediction markets, amid an uncertain end to the United States' war with Iran.

The warning was sent in an email last month, according to The Wall Street Journal. 

"Recent press reports have raised concerns about government officials using nonpublic government information to place wagers on online prediction markets, such as Kalshi or Polymarket," the email stated. 

The email, which was sent from the White House Management Office, explained that it's a criminal offense to use nonpublic information to buy or sell prediction-market contracts. 

The email was sent the day after President Donald Trump paused strikes against Iran. Heavy activity was seen in the markets 15 minutes before Trump made the announcement. 

The Journal noted that there's no evidence that anyone in the administration was using insider information to trade on the sites.