Davey Boy Smith - known to television wrestling fans as the British Bulldog - died on holiday aged 39.
He was initially thought to have suffered a heart attack after collapsing in British Columbia on 18 May.
His body was flown back to the UK for a post-mortem under the supervision of Greater Manchester Police, but more tests now need to be conducted.
Comeback bid
English police became involved after the wrestler's father, Sid Smith from Golborne, near Wigan, raised concerns about the circumstances of the death.
His son, who lived in Calgary, Canada, was on holiday with his girlfiriend when he collapsed.
Mr Smith became concerned after speaking to his grandchildren, Georgia, 13, and Harry, 15, the wrestler's children by his ex-wife.
Davey Boy Smith was on the verge of a comeback with World Wrestling Entertainment (WWE) - formerly the World Wrestling Federation - at the time of his death.
Millions of viewers followed the father-of-two's television exploits in the 1980s and early 1990s.
In 1998 he suffered a fall which left him with a spinal infection and it was feared he would never fight again.