Major League Baseball has determined the Boston Red Sox executed a scheme to illicitly steal hand signals from opponents’ catchers in games against the New York Yankees and others.

Brian Cashman filed a detailed complaint to the MLB last month.

The Yankees contended the video showed a member of the Red Sox training staff looking at his Apple Watch in the dugout and then relaying a message to players, who may have then been able to use the information to know the type of pitch that was going to be thrown, according to the people familiar with the case.

The commissioner’s office then confronted the Red Sox, who admitted that their trainers had received signals from video replay personnel and then relayed that information to some players.

Stealing signs is believed to be most effective when there is a runner on second base who can watch what hand signals the catcher is using to communicate with the pitcher and then relay to the batter any clues about what type of pitch may be coming. Such tactics are allowed as long as long as teams do not use any methods beyond their eyes.