Sheffield on Wednesday are investigating the pre-contract agreement which confirmed that midfielder Liam Shaw had signed for Celtic.
The 19-year-old, who came through the Yorkshire club academy, will move north to the Scottish Premier League this summer.
Before assistant John Kennedy stopped to move over from Hoops manager Neil Lennon last month, he spoke of Shaw, saying: “We are excited – another young player, who has good qualities, a good athletic player who plays in the middle of the pitch and who is also played at the back at times.
“Again, one for the future, a young player we see can come here and develop as do David (Turnbull) and (Ismaila) Soro as well.”
However, Wednesday released a statement on their official website stating that they were “investigating this matter” and saying that Celtic had been silent on a proposed co-ordinated release. .
Read the statement: “Sheffield on Wednesday can confirm that midfielder Liam Shaw has signed a pre-contract agreement with Scottish Premier League side Celtic.
“We are currently investigating this matter and will consider whether further measures are available to protect the club’s interests.
“It is not our intention to place this development in the public domain in terms of respect for all parties involved.
“However, Celtic contacted us informing the club that they intended to formally confirm this development, which was announced by the former Celtic manager in a media release.
“The two clubs exchanged statements prior to their co-ordinated release but Celtic have ceased to engage in this.
“Shaw will remain a Sheffield player on Wednesday until his current contract expires and he will be available for selection for the remainder of the season.
“We will not comment further at this time.”
Celtic have been approached for comments, but do not wish to do so at this time.