Doug Fister's decision to hang a mouthguard around his ear reportedly contributed to the New York Yankees' suspicions that the Boston Red Sox were cheating.

A report published Tuesday alleges the Red Sox were caught on video using an Apple Watch to steal signs from the Yankees after New York general manager Brian Cashman filed a complaint with Major League Baseball in August.

The Yankees reportedly also complained to the league after Fister's start Friday, suggesting the mouthguard hanging around the Red Sox pitcher's ear in the Yankee Stadium dugout was an illegal audio device, baseball sources told CSNNE's Evan Drellich.

Sources: Yankees complained to MLB when they thought Doug Fister had audio device. His mouthguard was around his ear https://t.co/gzrX9L58Pd pic.twitter.com/HFgimj7JWJ — Evan Drellich (@EvanDrellich) September 6, 2017

Both teams have attempted to fault each other for sign-stealing since the original complaint, though Yankees skipper Joe Girardi denied Boston's allegation that the Bronx Bombers used TV cameras in the stadium to pick up pitches by the Red Sox.

Commissioner Rob Manfred said Tuesday he does not consider the allegations "an ongoing issue," though he said the league is conducting a "thorough investigation" into the matter.