NAPERVILLE (STMW)– A fire investigation after the death of an elderly Naperville woman last month is over, with officials determining the blaze was accidental, but an exact cause remains undetermined, fire officials said on Wednesday.

While the woman, 82-year-old Lorraine C. Studin, was found with “overwhelming burns” to much of her body following the March 24 blaze, she died “as a result of coronary artery thrombosis” — or hardening of the arteries, according to autopsy results recorded April 12 at DuPage County Coroner Pete Siekmann’s office.

Burns, smoke inhalation and other fire-related trauma did not figure in Studin’s death, a spokeswoman for Siekmann’s office said. The autopsy also found no traces of alcohol or narcotics in her system, the spokeswoman said.

Siekmann and Deputy Naperville Fire Chief Rick Sander have said they believe foul play was not involved in Studin’s death.

On Wednesday, the Naperville Fire Department Fire Investigation Team announced the investigation into the cause and origin had been completed. And although an exact point of origin could not be determined, the “area of origin” was deemed a chair in the family room. It’s the same chair where Studin was found dead, a release from the department said.

Investigators said the probable cause of the fire was smoking materials. The fire is listed as “accidental” and the exact cause remains listed as “undetermined,” the release said.

The blaze engulfed the two-story house at 240 James Lane, where Studin lived with her husband, Anthony “Tony” Studin. The Studins were caught in a fire that erupted at 9:21 a.m. that day and gutted their house in the Kings Terrace area of Naperville’s east side.

Anthony Studin managed to escape through the attached garage. A fire official pronounced Lorraine Studin dead at the scene, after she was found in a ground-floor family room.

Anthony Studin was taken to Edward Hospital in Naperville and then flown by helicopter to Loyola University Medical Center in Maywood.

© Sun-Times Media Wire Chicago Sun-Times 2011. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed