Major League Soccer says it is investigating allegations of tampering by Inter Miami after the club signed Brazil midfielder Casemiro.

On Wednesday, Miami announced they had signed the 34-year-old - who left Manchester United at the end of last season - on a deal that runs to the end of the 2027 MLS campaign, with an option to extend until June 2029.

But moments later, the MLS released a statement saying it was "reviewing a tampering allegation" against the club.

"The league is gathering all relevant information and will refrain from further comment until the review is complete," it added.

"While Inter Miami CF and the LA Galaxy have reached a settlement for the discovery priority [first rights] to sign Casemiro, the terms will be released upon conclusion of the tampering investigation."

The investigation concerns Casemiro's discovery rights, an MLS regulation that gives a specific club first refusal over a player should they want to join.

A club may have up to five players on their discovery list at any time and can add or remove players.

Los Angeles Galaxy held the discovery rights for Casemiro but in announcing the player's signing, Inter Miami said they had acquired the rights from the Galaxy.

LA Galaxy said in a statement: "The LA Galaxy and Inter Miami CF have reached a settlement for the discovery priority to sign Casemiro, and the terms will be released upon conclusion of the tampering investigation currently open with Major League Soccer."

Casemiro announced in January that he would depart Old Trafford at the end of the 2026-27 season following a mutual decision not to renew his contract.

He won five Champions League titles with Real Madrid before moving to United in 2022, who played for Brazil as they reached the last 16 at this summer's World Cup.

"What motivates me the most, and I think this is true for every player, is winning and continuing to grow," he said.

Casemiro made 160 appearances for United, scoring 26 goals and providing 14 assists as he won one EFL Cup and one FA Cup.

In the wake of Casemiro's departure, United have prioritised midfield reinforcements in this window, buying Andrey Santos for £50m from Chelsea, and Youri Tielemans from Aston Villa for £35m.

Before the announcement of the investigation, Inter Miami co-owner Sir David Beckham said of Casemiro: "He is a winner who has achieved so much in the game and after such an incredible career with Real Madrid and Manchester United I'm delighted that he's decided to make Miami his next home."

At Miami, Casemiro is set to join former Real and Manchester United team-mate Sergio Reguilon as well as Argentina's World Cup finalists Lionel Messi and Rodrigo de Paul.

It is not the first time Inter Miami have been probed over transfer dealings.

In 2021 they were fined $2m after breaking MLS rules with the signing of France midfielder Blaise Matuidi from Juventus the previous year.

The MLS said Matuidi had been paid more than was allowed, effectively giving the team four "designated players" last season rather than the permitted three. Designated players' wages do not count towards the MLS salary cap.

Known as the 'Beckham rule', it was introduced when the ex-England captain joined Los Angeles Galaxy in 2007.