There's been a dramatic protest following Monday morning's Monaco Formula One Grand Prix won by Germany's Nico Rosberg.
The Red Bull and Ferrari teams have accused Mercedes of breaking the rules by carrying out secret tyre testing with Pirelli last week.
Stewards say they'll be sending a report to the sport's governing body the FIA, who could bring the matter before motor sport's International Tribunal.
Mercedes could face a heavy sanction, including possible exclusion from the championship, if it's found they've acted illegally.
Red Bull's Sebastian Vettel and Mercedes' Mark Webber finished second and third.
Vettel has 107 points, Raikkonen 86 and Alonso 78.