Transfers involving Samuel Eto'o and Willian in 2013 are part of a Premier League investigation into potential financial rule breaches by Chelsea.
Chelsea's owners say the allegations "pre-date the current ownership" and "do not relate to any individual who is presently at the club".
Chelsea were fined £8.6m by Uefa in July for breaking Financial Fair Play rules as a result of "submitting incomplete financial information" between 2012 and 2019.
The breaches were reported by the new owners, the Clearlake group, after the club's sale in May 2022 and it is understood they also notified the Premier League at the same time.