The age-old rivalry between the Boston Red Sox and the New York Yankees has just become a lot more heated.

In a report posted by the New York Times on Sept. 5, investigators for Major League Baseball (MLB) revealed that the Red Sox were illegally stealing hand signals from their opponents’ catchers during games against the Yankees. The Red Sox are currently ranked first place in the American League East, while the Yankees follow closely behind in second.

The controversy began two weeks ago when Brian Cashman, general manager of the Yankees, submitted a complaint with the commissioner’s office detailing specifics of the scandal. He included a video from a three-game series between the two teams in Boston last month.

The video showed a member of the Red Sox training staff using his Apple Watch to spread a message to the players in the dugout about the type of pitch that was to be thrown. The players then relayed this information to their teammates on the field, both up for bat and on the bases.

The Red Sox immediately responded to these accusations by filing their own complaint, alleging that the Yankees use a camera to relay signs during games. The camera belongs to the YES television network, which is co-owned by Yankee Global Enterprises.

Red Sox manager John Farrell claims he was informed that Boston players were trying to steal signs but did not know how they did. “I’m aware of the rule,” Farrell said in an interview with the New York Times. “Electronic devices are not to be used in the dugout. Beyond that, all I can say is it’s a league matter at this point.”

Stealing signs isn’t illegal in the MLB, but it’s strongly discouraged. However, the use of technology in order to see and relay the signals is prohibited. Just last year the MLB attempted to prevent the accessibility of information during games by banning smartphones and disabling internet capabilities of iPads and tablets. No mention has ever been made of Apple Watches, meaning that they’re technically still allowed.

For the player who is up to bat, recognizing the type of pitch is crucial. Stealing signs gives batters a clearer sense of where and when to swing, and when not to swing at all. It minimizes chance and enhances success. Noticing the other team’s signals is a tradition in baseball that is frowned upon, but unavoidable. However, the Red Sox just took this issue a whole lot further, and this time, the Yankees won’t let it slide.