CHICAGO—A judge has granted authorities permission to exhume the body of a Chicago lottery winner who was fatally poisoned with cyanide just as he was about to collect his $425,000 payout.

Cook County Circuit Court Associate Judge Susan Coleman signed off on the request Friday from prosecutors and the medical examiner.

Urooj Khan's July 20 death was initially ruled a result of natural causes. But a concerned relative asked authorities to look deeper, triggering further toxicology exams that led to the conclusion in November that the 46-year-old businessman was intentionally poisoned.

Police have not announced any suspects, and the man's wife denies any involvement in his death.

Medical Examiner Stephen Cina says he hopes to gather additional evidence through more tests on the body that could be presented in court.