"Major League Soccer has begun a formal review of Inter Miami CF's signing of midfielder Blaise Matuidi, specifically investigating whether the signing of the player complied with Major League Soccer's salary budget and roster guidelines," a league statement read.
"MLS will not make further comment until the completion of its investigation."
The club responded with a statement that read: "Inter Miami CF acknowledges the statement made by Major League Soccer today, and we look forward to fully engaging with the league's review process. We will have no further comment."
At the time of Matuidi's transfer, there was surprise that a player of his pedigree -- he won a World Cup just two years earlier -- was signed with the help of Targeted Allocation Money (TAM) and not as a Designated Player.
According to MLS's roster rules for 2020, this meant that Matuidi's salary was at least $612,500 but no more than $1,612,500. A source with knowledge of the situation indicated that the league is investigating whether Matuidi was paid additional money, with the knowledge of Inter Miami, in addition to what is specified in the player's contract.
"There are some concerns that Matuidi received additional dollars," the source said.
The source added that current Atlanta United Sporting Director Paul McDonough, who at the time of the deal was Miami's COO and Sporting Director, is not a target of the investigation.
Information from ESPN's U.S. Soccer correspondent Jeff Carlisle was used in this report