New Zealand rugby legend Jonah Lomu was reportedly on the waiting list for a kidney transplant at the time of his unexpected death.

The retired sportsman passed away in Auckland on Tuesday at the age of 40.

Lomu, who revealed in 1995 that he had been diagnosed with nephrotic syndrome, underwent a kidney transplant 11 years ago.

According to The Guardian, Lomu, who had regular dialysis, was waiting for a second transplant after the first failed.

The exact cause of the ex-rugby star's death has not been revealed.