Fareedun Ansari, 71, owes $124,000 in back taxes, the Chicago Tribune reported, citing records that show the Internal Revenue Service placed liens on Khan's house in Chicago nearly two years ago, as well as liens against Ansari in February and March 2011 for taxes related to a small business.
Ansari told reporters Thursday he had "absolutely nothing" to do with Khan's death, the Chicago Sun-Times said. Ansari's attorney, James Pittacora, said detectives had not interviewed his client.
Ansari was living at Khan's residence when Khan died suddenly in July at age 46, weeks after winning the lottery.
Khan's death initially was believed to have been the result of natural causes, but after a relative raised questions, extensive toxicological tests were performed and showed Khan died of cyanide poisoning. A hearing was expected Friday on exhuming Khan's body for autopsy, the Tribune said.
Police and prosecutors are investigating the death as a homicide and have not ruled out the possibility the killing was prompted by the lottery win.
A law enforcement source told the Tribune Khan died before he could collect his winnings, amounting to $425,000 after taxes.
Records show Khan's wife, Shabana Ansari, has been approved as the administrator of his estate, which, including the lottery winnings, is estimated to be worth $2 million.
Shabana Ansari, 32, says Chicago police questioned her after her husband died about what she had put in his last meal. She said she thinks investigators seized food from her home after toxicological tests showed Khan died from cyanide poisoning, the Tribune reported.
"He was such a nice person," she said. "No one would dare kill him."
Cook County prosecutors will request a court order Friday that Khan's remains be exhumed so the medical examiner can determine whether Khan ingested or inhaled the cyanide that killed him.
Chief Medical Examiner Stephen Cina told the Sun-Times, "I don't think it's going to change our cause and manner of death, but it could be helpful to police and the state's attorney's office if and when this case goes to trial."