Jill Sobule‘s death is receiving heightened scrutiny by investigators … because they’re trying to determine when she died — and if drugs, alcohol or carbon monoxide played any part.
A rep for the Ramsey County Medical Examiner in Minnesota tells TMZ … investigators are digging into the cause and manner of Jill’s death — and, a major detail investigators are trying to determine is whether she was still alive when a house fire broke out, where she was later found dead.

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Remember, Woodbury Public Safety received a call about an active housefire around 5:30 AM Thursday … with first responders arriving to find the house fully engulfed in flames.
Firefighters were actively battling the blaze while searching for a missing person — Sobule — who homeowners believed was inside … but, when they finally found her, Jill was already deceased.
The Ramsey County Medical Examiner rep also tells us that — in order to figure out if she passed before the fire, or because of it — Jill’s being tested for drugs, alcohol and carbon monoxide poisoning.
Both Jill’s manager and agent confirmed her death to us yesterday … remembering Jill as a “force of nature and human rights advocate whose music is woven into our culture.”
Sobule’s best known for her 1995 track “I Kissed a Girl,” “Supermodel” from the flick “Clueless” and the theme song to the Nickelodeon show “Unfabulous.”
She was 66.
RIP