(CNN) -- The body of an Illinois lottery winner was exhumed Friday by the Cook County medical examiner's office after toxicology results showed he died of cyanide poisoning.
An autopsy was performed on Urooj Khan's body, Dr. Stephen Cina, county medical examiner, told reporters.
It will take a few weeks for testing results and he could not predict the results, he said. Cyanide can evaporate after death, and it's possible it may not be present, he said.
Murder by cyanide poisoning is extremely rare, experts say.
Khan died in July, the day after the lottery issued him a check for about $425,000 after taxes. He won the money playing a scratch-off game a month earlier.
"We are investigating it as a murder, and we're working closely with the medical examiner's office," Chicago police spokeswoman Melissa Stratton said last week.
Cina said Friday, "We've already determined it was a homicide, and nothing we've seen today would change that."
On the day he died, Khan's wife said she made dinner at home and then he went to bed. A little less than an hour later, his screams of agony woke her up. His family rushed him to a hospital, but it was too late.
Initially, doctors ruled the 46-year-old died of natural causes. But later that week, an unnamed relative called the medical examiner's office.
"This person must have made a compelling case," Cina told CNN's Martin Savidge this month. "This was serious enough to order a full battery of toxicology, including unusual agents such as cyanide and strychnine."
The lab technician retested Khan's blood, and results came back in November. "It was definitely in the lethal range for cyanide in the blood," Cina said.
Cook County policy is not to perform autopsies on anyone under 50 unless the death is suspicious or an autopsy is requested.
Cyanide is among the most potent and deadly poisons, but it is not easy to get. The U.S. Consumer Product Safety Commission prohibits the retail sale of products with cyanide salts. It is, however, available from industrial sources. It cleans metal and is used in research labs and mining.
Cyanide can be found in some household products, such as acetonitrile false fingernail remover. There are also tiny quantities of it in cigarette smoke, and even smaller amounts in almonds, the pits of stone fruits such as apricots, and lima beans. Someone would have to eat a large quantity of those foods for them to become toxic.
"Like everything else, dose makes the poison," said Dr. Robert Geller, medical director of the Georgia Poison Center and an associate professor at Emory University School of Medicine. He co-wrote a study about cyanide poisoning and pediatric patients.
For someone to die from cyanide poisoning, he or she would have to inhale or consume a large quantity, which can cause a quick death, according to Geller.
If someone received a less severe exposure, such as through eating, the person would show early symptoms of weakness, confusion, headache, dizziness and shortness of breath. If untreated, the person could experience nausea, hypertension, vomiting, coma, seizure and then death due to cardio-respiratory arrest.
A person who has been poisoned with cyanide may take on a cherry-red coloring, and the retinal veins and arteries would appear red because the person's cells cannot get oxygen from the blood.
In a small number of cases, a patient's breath may smell like bitter almonds due to the excretion of unmetabolized cyanide, but more often than not it's undetectable, according to Geller.
"In terms of intentional poisonings, you don't have a lot of that with cyanide," Geller said. The Georgia Poison Center has handled more than 800,000 cases of poisoning, he said, and cyanide rarely turned up in those cases.
There is an antidote kit (PDF) available for cyanide, but doctors treating Khan would have had to suspect cyanide early in his treatment to use it.
"Because it is so rare and is used so infrequently, the medical profession may have a difficult time recognizing cyanide poisoning," Geller said.
The same is true after death. Scientists don't usually test for cyanide in the battery of toxicology tests they may run in a suspicious death and don't generally look for it unless there is a reason to suspect it.
Plus, there's an economic factor. "The harder you want to find something, the more expensive it is, and this country's forensic labs run on a shoestring budget," Geller said.
Even knowing that Khan was poisoned, it may be difficult to determine how the cyanide got there. "Cyanide does break down in the body fairly quickly, so they may not find much," Geller said.
"Now that he's been buried and embalmed, you don't have the ideal situation," said Dr. Daniel J. Spitz, a forensic pathologist and toxicologist and the chief medical examiner for Michigan's Macomb and St. Clair counties.
Spitz co-wrote the book "Medicolegal Investigations of Death," considered the bible of forensic pathology that pathologists worldwide use.
"If this were me, I'd be hoping with an autopsy every other cause of death is rejected," Spitz said. "You don't want to have a competing cause of death when you present your case in court."
In this next step in the investigation, scientists will examine Khan's brain, the liver and even solid organs to try to detect the presence of cyanide so they have more than one test showing it's what killed him -- and a better sense of how it was introduced into his body.
"Many people think, with this kind of poisoning being rare and something that may not be seen, that this would be a murder someone could get away with," Geller said. "But clearly it is not, since they did figure out this was cyanide, and there is a very good likelihood someone will get caught."