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.
The league’s investigation was confirmed in August and, as first reported by the Times, the signings of Cameroon striker Eto’o and Brazil midfielder Willian are being looked at.
Both players joined the club under the ownership of Russian oligarch Roman Abramovich, who was in control of the club from 2003 to 2022. They both signed from Russian side Anzhi Makhachkala.
Abramovich sold Chelsea to a consortium led by American investor Todd Boehly and private equity firm Clearlake Capital last year.
A Chelsea statement on Monday said: “These allegations pre-date the club’s current ownership. They concern entities that were allegedly controlled by the club’s former owner and do not relate to any individual who is presently at the club.
“Chelsea FC’s ownership group completed its purchase of the club on May 30, 2022.
“During a thorough due diligence process prior to completion of the purchase, the ownership group became aware of potentially incomplete financial reporting concerning historical transactions during the club’s previous ownership.
“Immediately following the completion of the purchase, the club proactively self-reported these matters to all applicable football regulators.
“In accordance with the club’s ownership group’s core principles of full compliance and transparency the club has proactively assisted the applicable regulators with their investigations and will continue to do so.”