Sale have made a complaint to the Rugby Football Union after information was allegedly leaked to opponents Bristol earlier this month.
Bristol fought back from 15-0 down to win the Aviva Premiership encounter 24-23 at the AJ Bell Stadium on New Year’s Day.
A spokesman for the RFU confirmed that the governing body was investigating the accusation, but no other details were given.
The spokesman said: “The RFU are investigating a complaint made by Sale Sharks in relation to the passing of information to the opposition team ahead of the match against Bristol earlier this month.”
Sale are next in action when they host the Scarlets in their final European Champions Cup group game on Saturday.
Bristol — who are bottom of the Premiership, seven points adrift of 10th-placed Sale — welcome Cardiff Blues in the European Challenge Cup this weekend.