Police are investigating alleged threats by Willie McKay towards senior Cardiff City officials, Telegraph Sport can reveal.

An inquiry has been launched amid accusations the man who booked Emiliano Sala’s doomed flight threatened to “kill everybody” at the club.

A complaint by Cardiff also claims he made similar threats against specific individuals, both in person and over the telephone.

Telegraph Sport has been told by sources close to the club that these individuals, who this publication has agreed not to name, are taking the threats seriously and have provided witness statements to that effect.

The police investigation is a major escalation in the acrimonious fallout from the fatal Jan 21 plane crash.

South Wales Police said that it “can confirm that a complaint has been received from Cardiff City Football Club and is currently being investigated”.

On conviction, a death threat is punishable by up to 10 years in prison.