Medical Examiner Stephen Cina said that within a week of Urooj Khan's sudden death a concerned relative asked his office to look closer, and in December his office determined that Khan died of cyanide poisoning, the Chicago Tribune reported Sunday.
Authorities are considering whether to exhume Kahn's body to try to determine how much cyanide he ingested or inhaled, Cina told the newspaper.
While a motive has not been found, police said they haven't ruled out that Khan was killed because of his big lottery win. The 46-year-old native of India forked over $60 at a convenience store on Chicago's Far North Side for two scratch-off ticket that turned him into a millionaire.
The amount of the payoff was not given.
An internal police document obtained by the Tribune indicated Khan came home from work on the night he died, ate dinner and eventually went to bed. He was later heard screaming and was taken to a hospital in Evanston, Ill., where he was pronounced dead, the document said.
Cina said no autopsy was performed on Khan because his death didn't appear suspicious and his age didn't trigger an automatic autopsy without an indication of foul play.
But a week later, a relative expressed concern about the results and asked for additional testing, the newspaper said.
"If a family member has a concern that seems valid, we take those seriously," Cina said. "We can't [ordinarily] look for every toxin under the sun like a 'CSI' episode [on television]."