MLS is investigating the signing of Blaise Matuidi by Inter Miami.
Matuidi joined Inter Miami on a free transfer in August.
"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."
The league is investigating whether Matuidi was paid with additional money beyond what was specified in his contract.
"There are some concerns that Matuidi received additional dollars," the source said.