As of last week, police had yet to interview McKay, who has already denied the accusations against him.
He also has a long history with Warnock, who told the Telegraph last month he had fallen victim to a “vendetta” over the pair’s links since Sala’s tragic death and denied they were “big pals”.
Cardiff on Saturday declined to comment on what is an ongoing investigation, having previously said: “It was necessary and appropriate for South Wales Police to be engaged on the matter.”
Among their accusations is that McKay threatened to “kill everybody” at the club on the same weekend as Sala’s funeral in Argentina a month ago.
He is alleged to have told officials: “I’ll kill everybody if my sons get slaughtered.”
McKay’s eldest son, Mark, was one of the agents involved in Sala’s transfer from Nantes to Cardiff, while another of his sons, Jack, helped make arrangements for the player’s doomed trip.
McKay has previously claimed he and his children – two of whom are Cardiff players – had “been through hell” over reprisals that followed the January 21 plane crash.