(CNN) -- The body of a million-dollar lottery winner will be exhumed for additional testing after toxicology results revealed the Illinois man died of cyanide poisoning, a judge ruled Friday.
Urooj Khan won the prize in June on a scratch-off ticket. The next month, he was dead.
Investigators initially ruled Khan's cause of death natural. But after being prompted by a relative, the Cook County medical examiner's office revisited the case and found a lethal amount of cyanide in Khan's system.
"That ... led us to issue an amended death certificate that (established) cyanide toxicity as the cause of death, and the manner of death as homicide," Chief Medical Examiner Dr. Steve Cina said Monday.
Authorities are hoping to use the exhumation to determine how the cyanide entered Khan's system. The exhumation is expected to occur Thursday, CNN affiliate WGN reported.
No arrests have been made in the case.
"We are investigating it as a murder, and we're working closely with the medical examiner's office," Chicago police spokeswoman Melissa Stratton said Monday.
Khan, 46, planned to use his winnings to pay his mortgage and bills, make a donation to St. Jude Children's Research Hospital and invest more in his dry cleaning businesses. The check, which amounted after taxes to about $425,000, was issued July 19, according to CNN affiliate WGN, but Khan never got to spend it.
The next night, Khan came home, ate dinner and went to bed, according to an internal police department document obtained by the Chicago Tribune. His family later heard him screaming and took him to a local hospital, where he was later pronounced dead, the paper reported, citing the document.
Chicago police haven't offered details, including a possible motive, about what they call an "ongoing investigation." Talking briefly with CNN affiliate WBBM and the Tribune, Khan's widow described her husband as kind and exemplary.
Jimmy Goreel, who runs the 7-Eleven where the winning lottery ticket was sold, offered similarly glowing comments about Khan.
"I would never think that anybody ... would hurt him," Goreel told WGN. "(He was a) nice person, very hopeful and gentle (and) very hard-working."
CNN's Greg Botelho and Chandler Friedman contributed to this report.